1. No category

Basics of Epistemology
Bryan Frances
The Basics of the Basics
The goal of this essay is to reveal some of the most important connections among the most important
concepts of epistemology: truth, belief, disbelief, suspension of judgment, degrees of confidence,
evidence, rationality, and others.
We begin with what may be the most central notion: belief. A belief is an opinion about things, a view
of how things are. But what does it mean to believe something is true, for instance, to believe that God
exists or that bees make honey? Answer:
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you accept those ideas (on some cognitive level)
you would bet on them as being very likely true
you have enough evidence so that additional evidence is unnecessary as far as you are
concerned
you have made up your mind and consider the case closed.
Beliefs can be positive or negative: the belief that I have a laptop is positive while the belief that God
doesn’t exist is negative. Beliefs can be utterly trivial: we all believe that 2 + 2 = 4 and that red is a color.
Others can be controversial: the belief that God exists. They can be serious: some of us think the capital
punishment system in the USA has caused great moral harm. Some are silly: we all believe that Winston
Churchill was not a church on a hill and that Earth is more than five minutes old. Some beliefs are held
for just a couple seconds and then discarded: while walking down a hallway at work you come to think
that someone moved the trash can in the hallway at work since yesterday; this belief leaves your mind
pretty quickly provided you don’t have occasion to think about it again. Other beliefs you have almost
your entire life: I believe that my name is ‘Bryan’. Some beliefs come from religion (the belief that
heaven exists), sports (the belief that the New York Yankees were the best team in baseball in the
1950s), ethics (the belief that third trimester abortion is wrong), politics (the belief that third trimester
abortion is legal in the USA), entertainment (the belief that Lady Gaga plays the trumpet), philosophy
(the belief that we don’t have free will), science (the belief that Venus is about the same size as Earth),
art (the belief that Michelangelo’s statue David is much better than almost all other statues), and just
about every other walk of life. Each of us has countless beliefs, many true and many false.
A belief, in the strict sense used in this essay, is something that is expressed by a complete declarative
sentence: it’s a claim, something that’s true or false, that someone thinks is true. If Kia says that one of
her beliefs is abortion, well she hasn’t really told you much of anything. Maybe she believes abortion
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should be legal. Maybe she believes it is morally acceptable. Maybe she believes both claims. In any
case, we need a full claim before we have a genuine belief, and saying ‘one of my beliefs is abortion’
isn’t a full claim; all it does is tell you a topic. Throughout this essay, whenever I talk of a belief I mean
something that is expressed by a complete declarative sentence.
Often I will use the letter ‘B’ to indicate an arbitrary belief. So when Jack believes bees make honey, and
I say ‘Jack believes B’, ‘B’ stands for the claim expressed by the declarative sentence ‘Bees make honey’.
If Jill believes that bees don’t make honey, then I would say ‘Jill believes not-B’, where in this context
‘not-B’ means the same as ‘Bees don’t make honey’.
Usually, it’s easy to determine if someone has a belief. Often all you have to do is find the right
opportunity to ask them. But other times it’s quite difficult. If Caucasian Chris is racist against African
people, does that mean he believes African people are inferior to Caucasians? He certainly acts that
way, virtually all the time, but if you ask him he may well vehemently deny that he is racist against
Africans or that he thinks they are inferior to Caucasians. Not all racists are aware of their own racism.
When it comes to human behavior, we want to say that he believes that African people are inferior to
Caucasians; but when it comes to ideas that he will explicitly agree with, we want to say he doesn’t
believe it although he acts it, so to speak. In this essay we will focus only on beliefs that people will
admit that they have.
On some occasions you hear someone contrast knowledge with “mere opinion”. When we say that a
belief is a “mere opinion” or “just someone’s opinion” usually we mean that the belief doesn’t amount
to knowledge and doesn’t have much evidence backing it up. In this essay, I use ‘belief’ in such a way
that I leave open whether the belief amounts to knowledge. So some beliefs have so much backing
evidence that they count as knowledge (e.g., we know that Jane Austen wrote Emma) whereas others
have no supporting evidence whatsoever (those are two extremes).
Here are some qualities we like our beliefs to have:
True:
Justified:
Knowing:
Productive:
it accurately reflects the way things really are
there’s something backing it up sufficiently
we don’t merely believe something but know it
they lead to new ideas, inventions, discoveries, and other useful things
We will be mainly concerned with the first three.
Here is a story that reveals some key connections among central epistemic concepts. There will be lots
of stories in this essay.
The Jury I. Jo is on a jury, deliberating on whether the defendant, the butler, murdered the maid.
The prosecutor’s presentations have been totally convincing. The evidence that he’s guilty is
overwhelming: he is videotaped in the room holding the bloody knife which is firmly embedded in
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the body, he had written in his diary that he was planning to kill her, there was a love triangle to his
detriment, etc. (Fill in the details as you like, using your novelist skills.) So, Jo the juror patiently and
competently considers the evidence and quite reasonably concludes that the butler’s guilty (so B =
the claim that the butler is guilty). But in truth he’s innocent: although he did indeed want to kill the
maid, and he had even planned on doing it, someone else murdered her and very cleverly framed
him. This kind of thing happens all the time. Only three people knew the truth: the butler himself,
the murderer who framed him, and the maid—who is no longer around to tell the truth. Suppose
Mo is another jury member. He has come to the opposite conclusion from Jo: he thinks that butler
did not murder the maid (the belief not-B). There are lots of potential explanations for why he came
to the opposite belief not-B: he didn’t listen to any of the prosecutor’s evidence, he has some
irrational bias in favor of butlers, he hates the prosecutor, etc. Let us suppose that he heard and
understood all the excellent evidence of the butler’s guilt but thinks the butler’s innocent because
he loves butlers, he hates the prosecutor, and he can’t control how his emotions affect his opinions.
Jo has a false belief—it’s false because the butler didn’t do it while she thinks he did do it—but her
belief is entirely reasonable given the evidence she had. The evidence she has, supplied by the
prosecutor, is misleading in the sense that it leads one to disbelieve the truth—but it’s still powerful
evidence, the kind that’s strong enough to make one completely rational in coming to a false belief.
Hence, a false belief can be entirely rational.
Now notice that although Mo has come to believe the truth, he is definitely irrational in doing so. In this
situation, Mo, the butler, and the murderer all have the very same belief—the belief that the butler
didn’t kill the maid—but Mo has lousy overall evidence for it while the butler and the murderer have
excellent evidence for it. Hence, a true belief can be entirely irrational.
Notice also that this case shows that two people can have the same belief but one person is much more
confident in the belief’s truth than the other person: although Mo is reasonably confident the butler
didn’t kill the maid, the real murderer is much more confident that the butler didn’t kill the maid. We
typically express this fact by saying that Mo’s level of confidence in ‘The butler is innocent’ is lower than
the level of confidence the murderer has in that very same belief. (These levels of confidence are often
called ‘credences’.) Another example: I might be 90% confident that Mark Twain was left-handed
whereas you might be only 70% confident. These are not levels or degrees of truth. It has nothing to do
with truth. Twain was either left-handed or he wasn’t. (We will consider the objectivity of truth later in
this essay.) When someone says that she is about 90% confident that claim C is true, she isn’t saying
that C is 90% true. Instead, she’s saying that by her lights the odds that C is true are about 90 to 10 in
C’s favor.
That’s the first version of the murder-jury story. Now change the story a bit.
The Jury II. Although the prosecutor’s case is exactly as before, the butler’s defense attorney
presented excellent evidence that the butler was innocent. For instance, the butler was righthanded, had a broken right arm, had a weak left arm, and yet the murder was clearly committed via
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a very strong stab with a very big knife requiring quite a bit of strength. So how could he have been
the one to stab the maid? Sure, he was found leaning over the body with his hand on the knife, but
perhaps he was going to try to remove it; or maybe he just needed to feel it. In addition, his diary
suggests, although it doesn’t prove, that he was planning to kill her next week, not on the day she
was actually killed. Finally, he had noted in his diary that he recently purchased not a knife but a
potent poison that can dissolve in water and remain tasteless.
In this second scenario, with the competent defense attorney presenting good evidence that the butler
didn’t do it, the ever attentive Jo and the other jury members have a difficult case before them. After
all, they have been presented with excellent evidence for his guilt and excellent evidence against his
guilt. This case illustrates that there can be both positive and negative evidence regarding a belief: the
former is evidence for a belief while the latter is evidence against that same belief, where the belief is
‘The butler killed the maid’. Sometimes negative evidence regarding a belief is called counterevidence.
What you’re supposed to do when faced with a case where there is positive and negative evidence is
“weigh” them to see which side is stronger. If the two sides are roughly equal in quality—so the
evidence for ‘The butler did it’ is about as good as the evidence against ‘The butler did it’—then you
should suspend judgment, which means ‘Do not believe that it’s true and do not believe it’s false’.
Being a paradigm of rationality, in this second version of the story Jo suspends judgment on the butler’s
guilt.
Thus, it’s not true that if you give up your belief, then you adopt the other person’s view. If you start out
believing B but then suspend judgment (also called “withhold belief”), then that means you do not
endorse B and you do not endorse not-B. If you start out believing B but then adopt the other person’s
view, then that means you do not endorse B but you do endorse not-B. Thus, suspending judgment is
importantly different from adopting the other person’s view.
In addition, suspending judgment does not mean “make my decision for me”. I’m agnostic with regard
to whether God exists, but the last thing I’m going to do is believe what some person tells me to do in
deciding whether God exists.
There are two common kinds of case in which we should suspend judgment. In one kind of case, we are
faced with the question ‘Is claim C true?’ (e.g., ‘Did the butler kill the maid?’) and we have significant
evidence both for and against C that more or less cancel each other out and we are forced to admit that
the total, overall evidence doesn’t really point towards C’s truth or C’s falsehood. The second jury case
with the impressive defense as well as prosecution is an example of such a situation. In the other kind
of case in which we should suspend judgment, we are again faced with the question ‘Is claim C true?’
but we have no good evidence either way: we have no decent evidence for or against C. For instance,
faced with the question ‘Did the planet Venus ever have living bacteria on it?’ I haven’t the faintest idea
what the answer is. I know very little about Venus other than it’s about the same size as Earth, it’s
hotter, and it’s covered in gases. This information tells me next to nothing regarding whether it ever
had living bacteria on it. (I could find out a lot more with a few minutes of research, but then I’d ruin the
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example!) Other people may have excellent evidence either way (e.g., they might be astronomers), but
that would just mean that they have evidence that I don’t have.
Suspending judgment is often a temporary thing, as this story shows.
The Fork in the Road. You are walking through the woods on a path and come to a fork in the path.
There are no signs or other indications as to which path goes where. You have to make a decision
about what to do. What you would like is to know whether ‘The right path leads to our destination’
is true. (If you knew it was true, you’d pick the right path; if you knew it was false, you’d pick the
left path.)
You might reasonably choose the left path but you’d be foolish to believe that you have chosen the path
to your destination. You simply don’t know which path is the right one, and you have to live with some
uncertainty for a while. Only a fool has an opinion as to which path is the right one—even though you
will have to make a choice. Wisdom often requires us to say ‘The evidence we have is not good’. You
are forced to make a choice as to action—you have to pick a path—but you are not forced to make a
choice as to belief—as you can suspend judgment. In that respect action is very different from belief.
Despite all that, eventually you will get evidence as to whether you took the right path (e.g., after you
have followed the path right to your destination); so the suspension of judgment was temporary.
Other times the suspension of judgment might never end. For instance, astronomers might start out
thinking that Venus could never have had living bacteria on it. But then they discover a way that it
might have had bacteria on it but only a billion years ago. So, they suspend judgment. And this
suspension might last forever because they are well aware that there is no way to figure out whether
Venus actually had bacteria on it a billion years ago.
Suspending judgment doesn’t mean giving up and sitting on your hands. For instance, a doctor needs to
figure out how to treat a specific patient. She can either operate or use medications. She might decide
that the two options are equally good, all things considered (cost, pain, etc.). So if a colleague asked her
‘Which option is best?’ she would have to say that she doesn’t know. She has suspended judgment on
both ‘Operating is best in this particular case’ and ‘Medications are best in this particular case’. But that
doesn’t mean she isn’t going to do anything. She still has to treat the patient. So, she will probably
choose somewhat arbitrarily which option to take. And when she has chosen (e.g., the meds) that
doesn’t mean that she has stopped suspending judgment. She’s made a choice on what to do, but not
on what to believe. Suspending judgment ≠ not acting.
The stories we have just seen illustrate several key epistemological facts, ones that are absolutely
indispensible:
1. Beliefs can be positive, negative, trivial, controversial, silly, serious, short-term, long-term, and
concern just about any topic.
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2. Some beliefs are true while others are false. ‘The butler did it’ was false while ‘The butler didn’t
do it’ was true.
3. Evidence can be positive or negative. Positive evidence for a belief B is evidence that suggests B
is true; negative evidence regarding B is evidence that suggests B is false. In the second version
of the murder story Jo had both strong positive and strong negative evidence regarding the
belief that the butler did it.
4. One’s overall evidence is the combination of all one’s evidence regarding that belief.
5. Two people could have the same belief but one person’s belief is irrational while the other’s is
rational, due to the fact that the first person has weak overall evidence for the belief and the
second person has strong overall evidence for the belief. Hence, evidence can be weak or
strong (or somewhere in between). Mo’s belief that the butler is innocent is based on weak
evidence while the butler’s belief that the butler is innocent is based on strong evidence.
6. A belief is irrational and unreasonable and unjustified (we will use these three terms as
synonyms) when the believer’s overall evidence is not even close to being strongly supportive of
the belief; her belief is rational and reasonable and justified when her overall evidence is
strongly supportive of the belief. In the first version of the story Jo’s belief was rational and
Mo’s was irrational.
7. A belief can be entirely reasonable but false provided the person with the belief has excellent
overall evidence that supports that false belief. In the first version of the butler story Jo’s belief
in the butler’s guilt was reasonable but false. In that case, the evidence will be misleading—as
it leads one away from the truth—but it can still be quite powerful in supporting one’s false
belief.
8. A belief can be entirely unreasonable but true provided the person with the true belief has very
poor evidence that she is basing her belief on. In the first jury story Mo’s belief in the butler’s
innocence was irrational but true.
9. There are three basic cognitive attitudes one can take to a claim: believe it, disbelieve it, or
suspend judgment on it. In the first version of the story Jo believed while Mo disbelieved ‘The
butler did it’; in the second version of the story Jo suspended judgment on ‘The butler did it’.
Moreover, one can believe or disbelieve it to different degrees, as when one person is
extremely confident it’s true while another person agrees it’s true but isn’t as confident as the
first person that it’s true. Those differing degrees are different levels of confidence. Both Mo
and the murderer believed in the butler’s innocence, but the murderer was much more
confident of it than Mo was.
10. Suspension of judgment ≠ adopting the other person’s view.
11. In some cases suspension of judgment is temporary; other times it is permanent.
12. Just because you have to suspend judgment on some claim (so you don’t believe it or disbelieve
it) doesn’t mean that you can’t act on it (think of the doctor or fork-in-the-road stories).
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Evidence
We already went over positive evidence, negative evidence (also known as counterevidence), and total
evidence. But what kinds of positive and negative evidence are there?
There are lots of kinds of evidence. Without attempting to list every category or have the categories be
mutually exclusive, or worry about whether one kind of evidence “boils down to” another kind of
evidence, there are some common categories of evidence below.
Physical. This is a very common type of evidence—the kind we hear about when watching television
shows about detectives. “I would like to introduce a key piece of evidence in the case, a bloody knife.”
It’s easy to imagine Sherlock Holmes saying something like that. But there are very different kinds of
physical evidence. For instance, storm clouds are good evidence that a storm is coming; tree rings can
be excellent evidence that a fallen tree was over a two centuries old.
Testimony. When you meet someone and she tells you she has two brothers, she has “given testimony”
for the claim that she has two brothers. Clearly, this is not a formal case of someone giving testimony—
as is the case when she is in a court of law. But when you meet someone and she tells you about
herself, and you come to believe her (under normal circumstances), you come to know things about her.
You know, for instance, that she has two brothers. And you know this because she told you so; that’s
what testimony is. Another case: you’re in Manhattan and ask a stranger for directions to the Empire
State Building. She will typically know where it is, she’ll tell you how to get there, and as a consequence
you now know how to get there, provided you understood what she said. You acquired knowledge via
the testimony of the stranger. If challenged with something like ‘How do you know she’s got two
brothers?’ or ‘How do you know that that’s the way to the Empire State building?’ you would probably
reply with something like ‘She told me so’. Your evidence is the fact that she told you so, in the context
of a conversation in which you had no reason to doubt her.
It’s amazing how many of our beliefs are based on testimony. You know that you’re a Fordham student.
How do you know this? Answer: because people have told you so, usually in writing. And how do you
know that human babies don’t hatch out of eggs or grow on trees? Answer: testimony.
Expert Testimony. As you might guess, this category is not terribly different from the former one. You
can learn things from testimony from people who aren’t experts. For instance, I can answer lots of
questions about astronomy that a child might ask me even though I’m not an expert in astronomy.
Really, I’m just a competent conduit from the experts to the child (and like real conduits I can transfer
only some things successfully). When you want a reliable source of information about a topic, the
natural thing to do is ask a genuine expert, whether the topic is astronomy, history, chemistry, botany,
or whatever.
However, the ‘whatever’ leads to difficulties; I’ll go over four of them here.
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First, there is the obvious issue of domain specificity: if you know that Sara is an astronomer, then you
know that she is an expert on astronomy, but this implies nothing regarding her expertise in other areas.
That’s pretty obvious: just because she is an expert on things like stars and galaxies hardly means she
will be an expert in Mediterranean history or baseball or economics. However, there are tricky cases as
well. For instance, will she be an expert on Einstein’s theory of relativity? What about Quantum
theory? Suppose Katlin is an expert in botany: will she be an expert on evolution? If you don’t know
much about those fields, then you won’t know how to answer those questions.
Second, there are political difficulties. For instance, it’s pretty obvious who one should consult when it
comes to the scientific status of theories of our solar system, or plate tectonics, or the health-tobacco
connection: in each case one should ask the relevant scientists. And yet, for some culturally sensitive
topics non-experts can be fooled into not asking the relevant experts. Centuries ago religious people
were told by their religious leaders to ignore what the relevant astronomers were saying about the
layout of our solar system: the religious leaders insisted that the Earth was at the center while the
astronomers said it was the Sun. And just a few decades ago the tobacco companies expended
tremendous efforts in trying to hide or distort the scientific consensus that smoking tobacco is
unhealthy. Today we are going through the same old deception, with many oil companies trying to
confuse people about the massive consensus about the existence, causes, and threat of global warming.
No doubt, fifty years from now almost everyone will know that these companies are full of selfish liars,
just like in the tobacco case, but right now that knowledge is much less common, thanks to the
impressive disinformation campaign funded by the companies.
Something similar holds for the theory of evolution: although experts will tell you that the odds that that
theory is false are about as good as the odds that the New York Yankees baseball team will have a 160-2
won-loss record next season, people in the US (especially, compared to almost all other “first world”
countries) are continually deceived about it. For thirty years now Gallup polls have shown that around
45% of people in the US believe God created humans in the present form in the last 10,000 years or so,
and yet much of science’s success is utterly dependent on that very claim being completely false: if the
creationist claim were true, there’s virtually no way that science could be so successful. This case of
deception is different from the tobacco and global warming cases: it’s not as though a few religious
organizations know the truth but are intentionally deceiving the public. Instead, by and large what is
happening is that there is an unhealthy ideological source to the unintentional deception. It’s not
always obvious who to turn to as a legitimate expert, since dishonesty and trickery are real threats.
Third, there are lots of cases where there is genuine difficulty—independently of deception—in figuring
who, if anyone, is an expert. Who is an expert on God, or morality, or beauty? Or even movies? Over
the last forty years or so Roger Ebert was the most influential movie critic in the USA. But was he a
better judge of movie quality than you are? Well, it depends. If we are looking to him to tell us whether
we will enjoy a movie, then he might be completely unreliable, provided we have very different tastes.
In that case, he would not count as an expert. If we are looking to him to be a good judge of the artistic
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merit of a movie, then maybe he was an expert. It will depend on whether there are experts regarding
artistic merit! Are there?
That’s a hard question, one beyond the scope of this essay. Clearly, Roger Ebert knew a lot more about
the artistic genre of movies: its history, its categories, etc. That knowledge might have given him the
potential to be a better judge of artistic merit than me, who knows little about movies. But I suppose
that one could have all that knowledge he had and still be almost blind to the humor and emotional
qualities of movies, which would make one a poor judge of artistic merit.
Analogous remarks hold for moral judgments. It’s hardly clear who counts as an expert in morality.
Should it be a philosopher, as the subject of morality has been always been the province of philosophy?
Or, if morality comes from God, should religious experts be the experts on morality? And how on earth
are we to tell who is a religious expert? Just like in the movie case, there are going to be plenty of
people who are experts in the sense that they know a great deal about the history, practices, and beliefs
of many religions. That’s real expertise, no doubt about it. But that’s not to say that any of them are
experts about God, for instance. It might be the case that God exists but almost all religions are just
horribly wrong about God. Alternatively, maybe there is no God, which again would mean that religions
are horribly wrong.
We will consider the special issues that come up with regard to religion, morality, and aesthetics in the
next section.
Fourth and finally, experts often disagree with one another on the very topics they are experts on. One
group says B; another says not-B. Some contemporary physicists say that electrons and other particles
come from the dynamics of tiny strings; others say they don’t. Now, this is probably a disagreement
that will never bother you, as you don’t have any deep convictions regarding the nature of electrons.
But take an issue such as theism: the thesis that God really exists. The people who have examined the
putative evidence the longest and with the most care are philosophers. The results of their investigation
are particularly interesting: on the one hand, among philosophers there are plenty of theists, atheists,
and agnostics (the latter consists of those who suspend judgment on the thesis that God really exists);
but on the other hand a clear majority of philosophers are not theists. I don’t have any significant polls
to appeal to here, but I’ve been a philosopher for about twenty years and this is my impression, for what
it’s worth.1 So, no matter what camp you fall into—theist, atheist, or agnostic—you can congratulate
yourself by repeatedly reminding yourself ‘There are lots of genuine experts who agree with me!!’ But
are you going to conveniently “forget” that there are plenty of experts that don’t agree with you? In
other words, are you going to deceive yourself?
Memory. Although nearly everyone complains about the unreliability of memory, for the vast majority
of us it works amazingly well almost all the time. You may well misremember where you left your
1
One poll:
http://philpapers.org/surveys/results.pl?affil=Philosophy+faculty+or+PhD&areas0=0&areas_max=1&grain=coarse
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basketball, but you probably recall where you were born, what year it is, whether spring follows winter,
whether Hitler had anything to do with World War II, whether you were born in Saudi Arabia, etc. We
rely on memory, both short-term and long-term virtually every minute of every day, and it almost never
fails us. Do you recall where you live, or how to get some food, or where to take a piss? Thank your
memory every time. We complain about our memory only because the millions of times it works are
largely invisible to us, as we rely on it as a matter of course and no problems arise.
Mathematical Proof. Here are the prime numbers from 0 to 30:
2, 3, 5, 7, 11, 13, 17, 19, 23, 29
Here are the ones from another 30-point interval 1000 to 1030:
1009, 1013, 1019, 1021
You’ll notice that there are far fewer primes in the second interval compared to the first interval (4
compared to 10). There are fewer and fewer of them the higher the numbers get. Mathematicians of
old used to wonder: in the sequence of prime numbers, beginning with 2, is there a last prime number,
the one that is greater than all the other primes? The Greek mathematician Euclid proved that there is
no such number: the primes go on forever. He proved this with a bit of abstract reasoning. Everyone
came to agree with him. And their evidence was his proof.
It would be nice if in ordinary life we often had evidence as strong as Euclid’s proof. His was airtight.
Does it ever get that good outside of mathematics? Maybe, but not for the things we tend to fight over
in our disagreements.
Sensory. Many people think sensory evidence is incredibly good, even though it’s not perfect. When
Karla pocketed the jewelry, and you saw it happen, you thereby acquired fantastically powerful
evidence that she pocketed the jewelry. How do you know she did it? You saw it happen. Vision,
hearing, smelling, touching, and tasting are the cognitive powers we have that generate our best
evidence, setting mathematical proof aside. In fact, many philosophers throughout history have argued
that sensory evidence is the kind of evidence that all, or virtually all, other evidence comes from.
Reasoning. Jan knows the cat is either in the bedroom or the den. She looks in the bedroom and
doesn’t see the cat; she concludes the cat is in the den. That’s a very common and incredibly simple
piece of reasoning. Jan took two pieces of evidence and saw where they lead: what conclusion they
justify. It’s not enough to merely have evidence; usually one has to take that evidence and reason with
it to figure out what it comes to. Evidence is similar to data; and reason is similar to the processing of
data.
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So put, reasoning doesn’t fit nicely with the other categories: in many cases, it’s not so much a category
of evidence but something one does with evidence. But since it’s so important I had to put it in here
somewhere.
One more thing about reasoning that we need to get clear on is how ‘premise’ and ‘conclusion’ work. In
the cat argument there were two premises in Jan’s argument:
1. The cat is either in the bedroom or the den.
2. She’s not in the bedroom.
3. So, she’s in the den.
Claims (1) and (2) are the premises; (3) is the conclusion; (1)-(3) is the argument. The premises are the
parts of the argument meant to support the conclusion; the conclusion is the “point” of the argument,
the thing the arguer is trying to establish. There’s more on these matters near the end of this essay.
Internal experience. When I was in graduate school studying philosophy I recall waking up one day with
a strange sensation in my chest. It was so odd that I couldn’t even classify it as painful or merely odd. It
wasn’t serious as far as I could tell so I went to the university as I usually did. But by the time I got there
the sensation was growing and I was getting very worried. Again, I still could not tell if it was a pain or
not! My friend Martha Flynn was a nurse and she helped me go to the hospital. While I was there the
medical folks asked me lots of questions, just as you would expect. And I gave them answers.
Amazingly enough, they actually believed me while I was telling them what I thought about my medical
condition! Me! A complete novice when it comes to anatomy was telling the distinguished doctors
what was going on! But they are the experts on anatomy and disease, not me, so why were they taking
my word for it?
Obviously, these questions are silly. They took my word for it because they trusted me to have
knowledge of what I was talking about. And I was expert on what I was feeling because, of course, we
are all pretty good judges about our own internal sensory feelings such as aches and pains. This doesn’t
mean that we are experts on their causes. In fact, I was at the hospital in order to ask the medical
experts about what is causing the internal sensation, how serious it was, and what to do about it. (It
turned out to be pericarditis, which eventually “went away”.)
I had internal sensory experiences that indicated that there was something physically wrong with me. I
had good evidence that there was something wrong with me, where the evidence was the sensory
feelings. The sensory feelings were just like physical evidence: a video of the butler holding the knife
that is plunged into the maid’s chest—the physical video itself—is evidence for the claim that he
murdered her; the internal feelings I was experiencing were good evidence that there was something
wrong with something in my chest. In that respect, internal feelings can count as evidence.
Please don’t get carried away with that slogan ‘internal feeling can count as evidence’. None of what I
have said above gives the slightest credibility to “feelings” like ‘I just knew he had had an accident; I
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could feel it in my soul’ or ‘I knew the Yankees were going to win! I could feel it in the air!’ Whether or
not a person can have internal feelings that count as powerful evidence for various religious or moral
claims is an issue we will return to below.
The Objectivity of Truth
In order to introduce some further epistemological facts, consider another story.
Left Hand/Right Hand. Carl thinks the brilliant 17th century scientist Issac Newton and the great 20th
century inventor Thomas Edison were left-handed. He thinks this because he knows that both of
them were geniuses (like most of us he heard this through his elementary school teachers) and he
thinks all geniuses are left-handed. But that latter idea is false: there have been plenty of geniuses
who weren’t left-handed. Now, no one has ever said to Carl ‘All the geniuses are left-handed’. But
he has heard over the years that lots of geniuses are left-handed—more than those who aren’t so
intellectually gifted. This bit of information is true: the percentage of geniuses who are left-handed
is greater than the percentage of other folk who are left-handed. So although Carl learned some
true information about geniuses and left-handedness, he extrapolated incorrectly in coming to think
that all geniuses are left-handed.
Carl has made a mistake in reasoning. It happens. He started with ‘Lots of geniuses are left-handed’,
which is true, but he made a mistake when that belief “morphed” into ‘All geniuses are left-handed’.
That’s where his mistake in reasoning happened. It would be going too far to say he did something
stupid; that would be too harsh a charge to level at him. But he did make a mistake. Note that later,
when he concluded ‘Newton and Edison were left-handed’, he didn’t make a mistake in reasoning.
Given that he believed that all geniuses are left-handed and Newton and Edison were geniuses, it was
quite reasonable for him to conclude that Newton and Edison were left-handed. That latter bit of
reasoning was good, even though it was based on a mistaken starting point (the starting point being the
idea that all geniuses are left-handed).
So here are some of Carl’s beliefs:
1.
2.
3.
4.
5.
6.
Lots of geniuses are left-handed—a greater percentage than those who aren’t geniuses.
All geniuses are left-handed.
Newton was a genius.
Edison was a genius.
Newton was left-handed.
Edison was left-handed.
He obtained belief 1 over the years, most likely in school as a child. Eventually, he came to have belief 2,
which more or less came from belief 1: belief 1 morphed into belief 2, and that was his prime error.
Belief 1 is true; we know this because people have done investigations to find out the rough percentages
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of left-handed people there are in the general population as well as in the group of people who are
geniuses. Belief 2 is false, as there have been a great many geniuses who were right-handed (not to
mention the geniuses who were ambidextrous). Beliefs 3 and 4 are clearly true, as history shows
(although they were geniuses in very different ways). What about beliefs 5 and 6?
Well, in order to figure out whether 5 or 6 were true we would have to stop considering Carl and start
considering Newton and Edison. When trying to figure out whether Carl’s beliefs 5 and 6 are true it
does not matter one bit what Carl thinks, what his reasons are, what his history or experiences are, what
his gut instincts are, or anything else of the sort. Carl is utterly irrelevant to the truth or falsity of his
beliefs 5 and 6.
In that sense, truth is objective: whether or not beliefs 5 and 6 are true isn’t affected by anyone’s
opinion about how Newton or Edison wrote. It’s not even dependent on what Newton or Edison
happened to think! Whether or not Edison was left-handed has to do with how he used his hands; it
doesn’t matter what he thought about his hands.
Suppose Edison always wrote with his right hand, never used his left, and used his right hand in an
entirely natural and easy way starting from when he first picked up a pencil or crayon as a child. But
imagine that he always told everyone he was left-handed. Pretend that he never wrote anything in
public, but always had one of his assistants write things on blackboards for him when he gave
presentations. Finally, imagine that somehow, through some cognitive quirk, he had actually convinced
himself that he was left-handed despite the fact when he was alone he always wrote with his right hand.
(Delusions can be quite powerful, even in smart people.) In that scenario, would he have really been
left-handed?
Obviously not. It would mean that he’s right-handed but has fooled everyone, including himself, into
thinking he’s left-handed. Again, it doesn’t matter what people think about how he used his hands;
what matters is how he actually used his hands. Truth is objective. When trying to answer the question
‘Is X true or not?’ the answer to the other question ‘Do people think X is true?’ won’t matter.
When I say that truth is objective, I’m not saying that all objectives truths are known, or even knowable.
An objective truth, in the sense we are using ‘objective’, is not a truth that has been proven true. All
that is meant by ‘X is objectively true’ is that whether people think X is true doesn’t matter as to
whether X is actually true.
I think that’s right, truth is indeed objective, but there are tricky cases that force us to be careful when
thinking about the objectivity of truth. Lady Gaga is famous in the USA. That’s just a fact about how
things are in 2012. In 2001 she wasn’t famous and in 2099 almost no one will remember who she was,
but right now, as I write this book, she’s famous. She’s not famous in some parts of the world (say,
Ethiopia), but in the USA she is famous. But now here’s the key thing: the truth that she’s famous is
affected by what people think. Not only that: the truth that she’s famous is entirely determined by what
people think. She’s famous because so many people, in the USA in 2012, are aware of her, and of
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course awareness has to do with thinking. This is very different from the Edison/Newton case, in which
the fact that Edison was right-handed isn’t affected in any way, shape, or form by what anyone thinks
about anything.
Really, though, the two cases are the same despite the contrary appearances. Whether or not Lady
Gaga is famous doesn’t depend on whether anyone thinks she’s famous. Instead, it depends on
whether people are aware of her. They don’t have to be aware of her fame; they need to be aware of
her. If almost everyone in the USA in 2012 knew who she was, but mistakenly thought that not many
people knew of her, then she’d be famous even though almost no one thought she was famous. So the
truth that she’s famous is still objective: whether it’s true that she’s famous doesn’t depend on whether
people think it’s true, even though whether it’s true does depend on what other thoughts people have—
namely, whether enough people know who she is.
Religion, Morality, and Objectivity
Thus, the Lady Gaga story doesn’t show that truth isn’t objective. But what other truths? Are any truths
subjective? For instance, what about religious truths?
Most Christians think Jesus rose from the dead; that’s obviously a religious belief. But this hardly seems
like a subjective matter. Either a certain guy, Jesus, rose from the dead around 2000 years ago or not.
What people happen to think about his life hardly matters to whether he really did rise from the dead.
Whether or not he rose from the dead is as objective as whether he was left-handed, whether he ever
had insomnia, or whether he knew how to wiggle his ears.
The same holds for the prime theistic belief: whether God exists. Again, whether people think God
exists is hardly relevant to whether or not he really does exist. Now, if you put a strange interpretation
on ‘God’, for instance thinking that God is just a concept or other idea that gives people meaning in their
lives, then whether “God” exists obviously is dependent on what people happen to think. But few
people think of ‘God’ that way.
So I’ve just argued that religious beliefs are objective. And yet, people are constantly saying that
religious beliefs are subjective—and it certainly appears as though they are saying something that has a
lot of truth to it. The key here is that the term ‘subjective’ gets used with several meanings. Often when
we say that religious views are subjective we mean things like the following, each of which is a
reasonable thing to say:

The beliefs have no solid, knock down proof.

We tend to be tolerant of the beliefs: if you say that there are tigers that roam Canada, people
will ask you for evidence; but if you say that Jesus rose from the dead almost no one will give
you a hard time about it.
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
Whether or not people accept a certain religious belief depends not so much on the evidence
but on what kind of person they are and what kind of life they have lived: what experiences they
have had, what culture they come from, etc.

Many religious beliefs are actually value judgments such as ‘Abortion is morally wrong’, which
are subjective in the sense that whether they are true depends on what people think and do and
feel.
None of those ideas is inconsistent with what I wrote above about the objectivity of the truth of
religious claims. I’m suggesting that most religious beliefs are objective when it comes to truth; the four
bullet points are consistent with that thesis: my thesis can be true even if all four bullet points are true
too.
So perhaps a great number of our religious beliefs are either objectively true or objectively false. What
about moral judgments (as in the fourth bullet point)? Are they objectively true or objectively false or
are they just subjective?
Here things get really complicated, deserving of a whole book instead of a few paragraphs. For starters,
many but not all people will say that moral judgments are like the Lady Gaga case: whether or not a
moral judgment like ‘Third trimester abortion is morally acceptable in most cases’ is true depends on
what people think and feel—how instances of abortion affect us, over both the short-term and the longterm—but it doesn’t depend on what people think or feel about the question ‘Is third trimester abortion
morally acceptable in most cases?’ That is, whether or not third trimester abortion is morally
acceptable depends on objective facts about how it affects us—just like how whether or not Lady Gaga
is famous depends on objective facts about what people know about her. Even if almost everyone in the
USA in 2013 said ‘Lady Gaga isn’t famous’, they could be wrong provided unbeknownst to them almost
everyone in the USA in 2013 did indeed know about Lady Gaga; to that extent ‘Lady Gaga is famous’ is
perfectly objective, as it can be true regardless of whether we believe it’s true. Analogously, even if
almost everyone in the USA in 2013 said ‘Third trimester abortion is morally acceptable in most cases’,
they could be wrong provided that unbeknownst to them such abortion cases affected us very
negatively; to that extent ‘Third trimester abortion is morally unacceptable in most cases’ is perfectly
objective, as it can be true regardless of whether we believe it’s true.
In that paragraph I assumed that whether something is morally acceptable depends on how it affects us:
whether it makes us happy or helps us flourish or increases our well-being. But many people have
thought that whether something is moral depends on what God commands, or on some rules such as
the Golden Rule of “treat others as you would want to be treated”. I’m not going to say anything
regarding who is right about the ultimate nature of morality! However, when it comes to the objectivity
of morality, many of these alternative theories say that moral judgments are objective in the same sense
as before. For instance, if everyone thought doing X was immoral but God had actually made a
commandment that we do X (and we had misunderstood his rule), then we would all be wrong about
what is moral to do; morality is objective in the sense that it’s not up to us at all.
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Despite all that, there are still other theories about the nature of morality that suggest that whether a
moral judgment such as ‘Third trimester abortions are morally acceptable in most cases’ is true does
depend explicitly on whether people think it’s true. This is a kind of moral subjectivism. But most
people cringe at such theories. They object ‘But if that were true, then if a community was severely
brainwashed into thinking it’s morally okay to torture kids for fun then it would morally okay to do so in
that community!’ And then they say that since it’s never morally okay to torture kids for fun, moral
subjectivism is false. I won’t be delving into any moral philosophy in this course.
Evidence, Objectivity, and Explanation
What counts as evidence is a tricky matter. Specifically, it is easy to find yourself pulled in opposite
directions regarding the objectivity of evidence. A story will illustrate the tension.
Forearm Hair. Bubba thinks men with long hair on their forearms are highly intelligent. He believes
this because as a kid the two men he admired most had long forearm hair. Neither of these men
was intelligent, but Bubba didn’t know that and he admired them anyway. Bubba is not very bright.
Now he meets Bartholomew, who has long forearm hair in addition to his long name. Naturally,
Bubba comes to think Bart is highly intelligent. And if you challenged him, Bubba would point to
Bart’s forearm hair as evidence that supports his belief.
But does Bart’s long forearm hair count as good evidence for Bubba’s belief? In one sense, no. The
reason: there is no real connection between long forearm hair and high intelligence: people with long
forearm hair are not more intelligent than people who don’t have long forearm hair (no matter how you
interpret ‘long’ or ‘intelligent’!). Bubba thinks there is a connection, he thinks he’s got real evidence, but
he’s wrong about that.
Consider an analogous case. It’s 7am and we are getting ready to go to work. We are wondering
whether it’s going to rain today. You look outside and see storm clouds. Well, that’s decent evidence
that it’s going to rain that day. It’s not conclusive evidence, but it’s pretty good evidence. It’s pretty
good because of this fact: the odds that it’s going to rain are considerably higher if there are storm
clouds in the sky than if there are no such clouds in the sky. So the fact of storm clouds is good evidence
because it increases the likelihood that our belief that it’s going to rain is true. But in Bubba’s case, the
fact of long forearm hair is not good evidence because it does not increase the likelihood that Bubba’s
belief in Bart’s intelligence is true. In general, it’s pretty rare that thinking you have X (e.g., good
evidence) automatically means you really do have X!
So in one sense of ‘evidence’, an objective one tied to the idea that evidence increases the likelihood of
(objective) truth, Bubba has no evidence that Bart is highly intelligent.
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On the other hand, doesn’t it seem that Bubba is doing something right when he concludes that Bart is
intelligent? Even if forearm hair has nothing whatsoever to do with intelligence, it seems like Bubba is
doing something correct in coming to think Bart is intelligent. Well, what is that something that’s
correct?
Here’s one thing he’s doing right: given that Bubba thinks long forearm hair is good evidence for
intelligence, he would be irrational if he didn’t come to think Bart was intelligent! After all, (a) he thinks
anyone with long forearm hair is intelligent, and (b) the only thing he knows about Bart is that he has
long forearm hair. Given (a) and (b) Bubba would have to be pretty foolish not to come to think Bart is
intelligent. He is doing the reasonable thing given his initial beliefs.
Moreover, maybe when he was a kid he was reasonable in coming to think that long forearm hair meant
high intelligence. Sure, that sound odd, but stranger things have happened. Maybe he was young and
really thought that X and Y were the two smartest people he knew and both had really long forearm
hair. Maybe he never had occasion to rethink his belief in the tie between forearm hair and intelligence,
even though a moment’s reflection would tip him off: ‘Wait a minute: does long forearm hair really
mean high intelligence? Where did I get that idea?’
Thus, just because Bubba fails to have good evidence for his belief doesn’t mean that his coming to have
that belief is epistemically horrible all the way through.
The Bubba story is somewhat silly, as no one thinks forearm hair indicates intelligence—although it’s
worth noting that some people still mistakenly if implicitly think that being tall or rich or a white male is
a good indicator. But the lesson is serious. Consider the fact that many people think their gut feelings
count as good evidence for some of their beliefs, especially their moral and religious ones. Many people
also think that their own life experiences count as powerful evidence for those beliefs. But even though
people say this, that doesn’t mean that what they’re saying is really true. It might be the case that gut
feelings and experiences count for next to nothing when it comes to evidence for or against religious
beliefs: the feelings and experiences are about as good evidence as the long forearm hair—namely, not
good at all. On the other hand, perhaps they count as quite strong evidence.
We must distinguish objective evidence from explanation. Another story will help.
Wasps Make Honey. Jerry thinks that wasps make honey. He also thinks that bees make honey,
which of course is a very common belief, but he thinks wasps make honey as well. There is a good
explanation of why he came to have this odd belief, an explanation that goes as follows. As a child
he learned that bees make honey. Then he learned that wasps were like bees in that both can sting
you. He figured that wasps must make honey just like bees, as bees and wasps are pretty much the
same thing. That’s all there is to it: that’s the whole explanation of how he came to think that wasps
make honey.
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There you have it: an accurate explanation of how Jerry came to have a certain belief. But just because
we now understand why he has that belief, this does not mean that we have learned what evidence he
has for his belief. As things stand, he has nothing even approaching decent evidence for his belief that
wasps make honey. Just because he has reasons that he bases his belief on—if you asked him for his
reasons, he would say ‘Well, bees make honey and wasps are just like bees; so wasps must make honey
too’—doesn’t mean that those reasons count as evidence. Reasons why someone has a belief can be
evidence, but they need not be. Reasons can be good and they can be bad; Jerry’s are bad. The
Forearm story also illustrates this: we have an informative explanation of why Bubba came to think Bart
was highly intelligent, but that didn’t mean he had objectively good evidence for his view.
This explanation/evidence distinction is important. After all, someone might have religious or
philosophical beliefs because he interpreted some tea leaves in a certain way, or because in his favorite
fantasy book (that he worships) that belief is true, or because he desperately wants it to be true, but
that hardly means that he has evidence for his belief. If his tea leaves tell him that he has an immortal
soul, that hardly means that he has evidence that he has an immortal soul. Of course, we all may in fact
have immortal souls, and some people may have genuine evidence that we have immortal souls, but just
because there is an explanation of why so-and-so thinks he has an immortal soul doesn’t, all by itself,
mean that he has any evidence for that belief: again, explanations need not amount to evidence.
Therefore, an explanation of why so-and-so has a belief need not, although sometimes it does, appeal to
any evidence she has for that belief: she may have no evidence for it.
Knowledge and Justification
Knowledge is probably the most important notion in epistemology; justification (or rationality, or
reasonableness) comes second. How they relate to belief, evidence, and other epistemic notions (and
one another) is one of the perennial topics in philosophy. In this section I go over the basics of
knowledge; justification is treated in the next section.
I know how to throw a curve ball. I also know Minneapolis, as I once lived there for ten years. I know
where the island of Cyprus is, since I spent a summer there. I know what’s on my bedside table: epic
fantasy and horror books. I know when Henry Aaron broke Babe Ruth’s home run record: 1974. I know
that water contains hydrogen. I know why she left him: she found out he really didn’t love her. I know
who fed the cat: Alec.
Paying attention to grammar, we can see from the previous paragraph that there is knowing-how,
knowing-an-object, knowing-where, knowing-when, knowing-that, knowing-why, and knowing-who.
These are not kinds of knowledge, but something like different grammatical categories, or differing
grammatical indicators of the general category of knowledge.
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Over the centuries, philosophers have spent most of their energy investigating knowing-that. We will do
so as well. The reason for this historical emphasis, I suspect, is that philosophers think knowing-that is
both the foundation of many of the other categories (e.g., knowing-that is somehow the foundation of
knowing-who) and is tied to truth, which is another key philosophical notion.
Let’s return to Carl in the Left Hand/Right Hand story, who you’ll recall thinks both Newton and Edison
were left-handed, and he thinks this because he thinks that all geniuses are left-handed. As a matter of
fact, Newton was left-handed and Edison was right-handed. So his Edison belief was false (that’s belief
6) while his Newton belief was true (that’s belief 5). Some beliefs are true while others are false.
How is belief related to knowledge? For instance, does either of Carl’s beliefs amount to knowledge?
That is, does he know that Newton was left-handed or that Edison was left-handed?
Most people would answer both questions negatively, but for different reasons. Take the Edison case
first. No one can know that Edison was left-handed because he was not left-handed. You can’t know
something that’s false. You can’t know that Barack Obama is a baseball player, or that Lady Gaga was in
the rock group Led Zeppelin, or that the Moon is larger than the Earth: you can’t know them because
they aren’t true. Knowledge requires truth.
Someone might object to this idea that knowledge requires truth. She might think that if virtually
everyone thought that X was true, and this belief was totally reasonable because they had no way of
knowing that it was false, then they could know it even if it’s really false. For instance, a long time ago
almost everyone thought the earth was stationary and the sun went around it once a day. Not only
that, but this belief of theirs was entirely reasonable, as it was based on perfectly intelligent observation
and there was no evidence at all that it was wrong. Given their lack of technology, they had no chance
to discover the truth. We now know that they were wrong, as the sun does not go around the earth
once a day and the earth is not stationary, but back then before astronomy kicked in everyone knew
that the sun went around the earth once a day. Knowledge is something like a belief that is entirely
reasonable and is such that the believer had no way to discover that it’s false, if it really happens to be
false.
Almost all epistemologists think that although that idea is reasonable it is usually based on a subtle
confusion: mixing up reasonable belief with knowledge. People thought they knew that the sun went
around the earth. And their belief was entirely reasonable, as they had genuinely good observational
evidence backing up their belief. But they didn’t really know it. There is a big and crucially important
difference between knowing something and having excellent overall evidence for it. Knowledge isn’t
merely being completely diligent, intelligent, careful, and doing one’s best to find the truth; one has to
get the right answer as well. In that sense, knowledge doesn’t just have to do with the believer but with
the aspect of the world that her belief is about. When Kiara knows that Tyrone aced the exam, this says
something about Kiara—she has a certain kind of awareness—but it also says something about Tyrone:
he really did ace the exam. Thus, knowledge isn’t justified belief.
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Therefore, epistemologists have almost always thought that knowledge requires truth and hence
justified belief isn’t the same thing as knowledge (since knowledge has to be true while justified belief
need not be true).
Most of them also think that knowledge requires good overall evidence. Earlier we saw that a person
could have a true belief that is irrational because it’s based on poor evidence (that was Mo thinking the
butler was innocent); analogously, one can have a true belief that fails to amount to knowledge because
it’s based on poor evidence. So Carl, who managed to obtain a true belief—the belief that Newton was
left-handed—did not have knowledge, as Carl’s evidence wasn’t good. We would say that in a certain
sense Carl got lucky in coming to a true belief about Newton. He had no real way of knowing that
Newton was left-handed, right? He believes Newton was left-handed, and that belief is objective true,
but he believes it for the wrong reasons, which means it doesn’t count as knowledge. In order to know
something two conditions have to be met: the belief has got to be true (as we saw above), and you have
to believe it for good reasons. If you believe it for bad reasons—for instance, because your horoscope
said so—then you don’t really know it. Knowledge is something like “getting things right because one
has genuinely seen the truth”. And in order to “genuinely see the truth” one has to believe it for the
right reasons. Knowledge requires justification.
Epistemologists, like almost all philosophers and other intellectuals, love a good fight (especially when
there is no blood or physical pain involved). They want to convince you that knowledge really does
require truth and good overall evidence. Although I have offered a quick explanation of why they think
knowledge requires truth and justification, I have definitely not proven it. An intelligent person could
quite reasonably be thinking to herself ‘Well, Professor Frances says knowledge requires truth and
belief, and what he says isn’t stupid, but I sure as hell am not convinced’. That’s the beginning of the
fight. But for our purposes in this course, we can avoid the fight entirely. It’s easy to see that there are
several different categories:
Believing something.
Believing something true.
Believing something on the basis of good overall reasons.
Believing something true on the basis of good overall reasons.
For our purposes, we will reserve ‘belief’ for the first category; ‘true belief’ for the second category;
‘justified belief’, ‘rational belief’ and ‘reasonable belief’ for the third category; and ‘knowledge’ for the
fourth category.2 We won’t spend time arguing that ‘justified’ and ‘knowledge’, as they are used in
contemporary English, really do, as a matter of linguistic fact, pick out those categories.
2
There is controversy regarding the equation of justified true belief and knowledge. For many centuries
many philosophers thought that every justified true belief amounted to knowledge and every instance of
knowledge was a justified true belief: justified true belief = knowledge. But in the 20th century
philosophers came up with some cases in which people seem to have justified true beliefs that do not
amount to knowledge. From roughly 1970 to 2010 people were generally convinced that those cases
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Given our notion of knowledge, it must be objective: just because someone thinks she knows something
doesn’t mean that she really does know it. She might have excellent overall evidence for her belief, and
she might be as rational as anyone ever gets, and maybe no one had any way of doing better than she
did in coming to her belief, but for all that her belief might be false anyway. And that would mean that
she doesn’t know what she thinks she knows. In that sense, knowledge is objective.
Some results about knowledge, continuing our list of results from earlier in this essay:
13. Knowledge requires truth: you can’t know something unless it’s true.
14. Knowledge requires good evidence: you can’t know something unless your belief is based on
good evidence.
15. Knowledge is objective: just because you or other people think you have knowledge doesn’t
mean that you really do have knowledge.
16. One can have a true belief without knowledge. Carl’s true belief that Newton was left-handed
doesn’t amount to knowledge (since it wasn’t based on good evidence).
17. One can have a belief backed up by excellent overall evidence that doesn’t amount to
knowledge: justified belief without knowledge. Jo’s completely rational belief that the butler
did it doesn’t amount to knowledge because it’s false.
Evidential and Prudential Rationality
The notion of rationality is ambiguous. Two stories will show this; here is the first.
The Tennis Player. Suppose Cat is an athlete who is getting “psyched up” for a game. Her coach
and other supporters are being as emotionally persuasive as possible to get Cat convinced that she
is invincible, will play her very best, and will defeat her opponent. Cat is playing in her first
Wimbledon tennis match against the top player in the game, who has won Wimbledon three times
in the last six years whereas Cat is ranked about 62nd in the world.
On the one hand, this is pure nonsense, right? She is far from invincible, there isn’t the slightest reason
she is going to play her best (what are the odds of that?), and she is almost certainly going to lose, since
her opponent has a much, much better track record in these games. Sure, there always is a chance that
Cat’s going to defeat the champion, but that truth does nothing to justify any of these claims, each of
which she believes at the start of her tennis match:
were genuine. As I write this, philosophers are somewhat less confident. In any case, we will not have
much occasion to address that controversy, as it won’t matter to our real-life concerns.
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a. I’m going to play my very best.
b. I am invincible.
c. I will win.
Going by the cool light of reason, her beliefs are baseless and irrational—especially beliefs (b) and (c).
That’s all true, and it’s important for any serious spectator of the game who is interested in knowing
who is going to win, but it’s only half the story. In order for Cat to play well today, she needs to be in the
right frame of mind. Frankly, unless she is deceived about her own prospects, she won’t play well!
Oddly enough, being irrational is exceedingly helpful to her: without it she won’t play nearly as well.
Given those psychological facts about Cat, it’s rational—in a certain sense—for her to think she is going
to win. In a real sense, the right thing for her to do is convince herself she’s going to win. This is not
rational when it comes to evidence, but it’s rational when it comes to her goals: having the belief that
she’s going to win is more beneficial to her than not having the belief (at least in the short-run; we don’t
even try to consider the benefits or costs over decades). In one sense, the evidential one, she should
not think she’s going to win (she shouldn’t have belief (c)); but in another sense tied to goal
achievement she should think she’s going to win. We call this latter kind of rationality prudential. Her
belief (c) is prudentially rational but not epistemically rational. In the prudential sense of ‘should’, she
should believe she’s going to win; but in the epistemic sense of ‘should’, she should not believe she’s
going to win.
The reverse case is common as well: beliefs that are epistemically rational but not prudentially rational.
Our second story illustrates this fact.
The Tobacco Community. Harriet lives in a place in the 1960s where tobacco is the source of almost
everyone’s livelihood—including her own. She is the only one in her community who becomes
aware of the strong causal connection between tobacco and cancer. Her coming to believe in that
connection causes her life to be filled with painful doubts, tensions, and eventually misery when she
voices her opinion to others, but the belief is supported by tons of evidence.
Her belief is epistemically rational—based on excellent overall evidence—but not prudentially rational,
as it is going to lead to all sorts of heartache for her. Hence, her belief is epistemically rational but not
prudentially rational, the reverse of the tennis case.
So, there are two quite different notions of rationality that apply to beliefs and actions. Let’s say that a
belief is prudentially rational when having it significantly contributes to the well-being of the believer.
A belief is epistemically rational when it’s based on excellent overall evidence.
Hence, we have a couple more results to keep in mind:
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18. A belief is prudentially rational when it will be highly beneficial for that person to have; a belief
is epistemically rational when it is based on strong overall evidence.
19. A belief can be prudentially rational but not epistemically rational (tennis story); a belief can be
epistemically rational but not prudentially rational (tobacco story).
Theories, Arguments, Premises, Conclusions
We need to understand some crucial vocabulary.
Here’s a theory T1 regarding the question of who killed the maid:
The cook did it; the butler had nothing to do with it. She killed the maid in the drawing room with a
knife because the maid had spurned her romantic advances.
Notice that the theory consists of several claims: (i) the cook killed the maid, (ii) she killed her in the
drawing room, (iii) she killed her with a knife, (iv) she killed her because she had spurned her romantic
advances, and (v) the butler had nothing to do with the killing.
Here’s another theory, T2, regarding the killing:
The butler did it; the cook had nothing to do with it. He killed the maid with a knife in the kitchen
and deposited the body in the drawing room. He killed her because the maid was blackmailing him.
This theory consists of multiple claims as well: (vi) the butler killed the maid, (vii) he killed her in the
kitchen and deposited the body in the drawing room, (viii) he killed her because she was blackmailing
him, and (ix) the cook had nothing to do with the killing.
Here’s an argument for some main parts of T1, the theory that the cook killed the maid:
a. The cook was seen hitting on the maid on several occasions by several witnesses. In each case
the maid rejected her.
b. The cook’s diary has multiple entries regarding the maid. They start off positive, with
descriptions of how much she loves her. But then they devolve into rants about the maid,
saying all sorts of awful things about her. Two days before her death, there is an entry about
how she’d ‘like to kill her’.
c. The maid was killed with a long knife.
d. The cook but not the butler had access to the long kitchen knives.
e. The butler hated the maid but had a very weak left arm.
f. The coroner testified that the murderer was left-handed and used a large knife to make a huge
fatal wound. Only a strong left-hander could have done it.
g. The cook was very strong and left-handed.
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That’s an argument for three conclusions: (i), (iv), and (v). The argument has seven premises, (a)-(g),
which are claims intended by the person giving the argument to supply strong support for the
conclusions.
Here’s an argument for some main parts of T2:
1. The butler had stolen several valuable items from the house. He had also billed the house for
several expensive items that he never bought.
2. The maid’s diary talks about how she found about and confronted the butler about this matter.
The maid admits, in the diary, to getting the butler to give her $5000 in hush money. And she
writes about how gleeful she is that she can continue to squeeze the butler for more money in
the future.
3. The butler has a history of breaking the law: two arrests for disorderly conduct at pubs.
4. The butler is an alcoholic who was drunk at the time of each arrest.
5. Although the butler has been a member of Alcoholics Anonymous, he has recently returned to
drinking, as several witnesses testify.
6. Although the cook did hate the maid for spurning her, the cook has no history of violence and
was well known to “talk big” and boast but never confront anyone in a manner that is anywhere
near violent. Several witnesses testified about how she has always been quite gentle.
That’s an argument for three conclusions as well: (vi), (viii), and (ix). The argument has six premises, (1)(6), which are claims that are intended by the person giving the argument to offer strong support for the
conclusions.
Thus, there are theories, arguments, premises, and conclusions:
A theory is a collection of claims, and those claims are meant to be supported by arguments that
consist of premises offered in support of conclusions, where the conclusions are the claims of the
theory.
In addition, there is the strength of an argument: the amount of support it gives to its conclusion(s).
Some arguments are good ones, as they give strong support to their conclusions; while other arguments
are bad ones, in that they give little or no reason to believe their conclusions.
Some arguments are perfect in this specific sense: if the premises are true, then the conclusion has
simply got to be true: there is no way at all for the conclusion to be false if the premises are true. This
argument has that feature:
P1:
P2:
C:
Either Tom is in the garden or he’s in the kitchen.
Tom is not in the garden.
Thus, Tom is in the kitchen.
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Arguments with that feature are called deductively valid. The two arguments above, regarding the cook
and the butler, were not deductively valid: one can imagine that the premises are true but the
conclusions are false. The argument about Tom isn’t like that: you can’t coherently imagine the two
premises being true while, at the same time, the conclusion is false.
So we have come up with some more results—and I’ve added a few we haven’t gone over:
20. A CLAIM is either a truth or a falsehood. Claims are expressed with full declarative sentences.
21. A THESIS is a particularly important claim. It’s one that is one of the highlights of an essay or
article, for instance, and is typically defended with arguments.
22. An ARGUMENT is a series of claims, one of which is the conclusion and the others are premises.
An argument is not a claim. It is not true and it is not false, ever. An argument can be good or
bad, but it’s never true or false. An argument is intended to show that its conclusion is true;
that is the purpose of an argument.
23. A CONCLUSION is the part of the argument that the argument is intended to support. The
argument is intended to show that the conclusion is true. A conclusion is a claim. If it’s
important enough, then it might be a thesis.
24. A PREMISE is a part of an argument that is supposed to help support the argument’s conclusion.
A premise is a claim. Premises are intended to work together to show that the conclusion is
true.
25. A THEORY is a collection of claims that are intended to give a more or less complete account of
something. A theory is like an individual claim in that it can be either true or false: it’s true
when almost all of its individual claims are true, and it’s false when almost all of its individual
claims are false. Some theories are known to be true, others are known to be false, and still
others are not known to be true and are not known to be false (e.g., the theory that head lice
jump from head to head is known to be false; the theory that human skin is made of cells is
known to be true; the theory that the universe had a beginning is neither known to be true nor
known to be false). When someone says that something is a “mere theory” usually that means
that it is a theory that is not known to be true and not known to be false. When someone says
that something is a “fact instead of a mere theory”, usually that means that it is a theory that is
known to be true.
26. A DEDUCTIVELY VALID argument is one that has this feature: if the premises are true, then the
conclusion must be true as well. The truth of the premises guarantees the truth of the
conclusion. There is no way whatsoever that the conclusion can be false provided that the
premises are true. This is not to say that the premises or conclusion are true in a deductively
valid argument! It’s just to say that if the premises are true, then the conclusion must be true
too. Notice that only arguments can be deductively valid. In particular, no claim can be
deductively valid! No premise can be valid. No conclusion can be deductively valid. No theory
is deductively valid. Don’t use ‘deductively valid’ as a synonym for either ‘true’ or ‘reasonable’.
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To say that an argument is deductively valid is to say that it has one particularly important and
good feature; but just being deductively valid doesn’t make an argument good in an overall
sense of being good.
27. A REFUTATION is an argument that proves that something really is false. Thus, a refutation is by
definition something that succeeds in showing that something is false. Thus, no one can refute a
true claim. One can disagree with a true claim, or dispute a true claim, or argue against a true
claim, but one can’t refute a true claim because to refute something is to successfully show that
it’s false—which would mean that it really is false. Note that a refutation is not a claim; it’s an
argument. Often, though, we can convey a whole argument with just one sentence; so the
connection between refutations, arguments, and claims is pretty tight.
28. What it means to EVALUATE a view (either a single claim or an entire theory) is almost always
this: one looks at reasons for thinking that the view is true, one looks at reasons for thinking that
the view is false, and then one tries to figure out which side is strongest. So when you’re asked
to evaluate a view (like in a philosophy essay), tell the reader the good reasons (if there are any)
for thinking that the view is true, tell the reader the good reasons (if there are any) for thinking
that the view is false, and then explain to the reader which side is the strongest—and give the
reader your reasons for thinking that you have chosen the strongest side.
29. A belief is RELATIVE when it is true with regard to one thing but false with regard to something
else. That’s not informative, but a bunch of examples should help. For instance, my belief
“Crème brûlée is the best dessert” is relative because although it’s true relative to my taste buds
it’s false relative to my son’s taste buds. My belief “Pennsylvania is about a 100 miles away” is
true relative to my present geographical position but false relative to many other geographical
positions. My belief “Fred is standing to the right of George” is true relative to my present
spatial orientation but false relative to many other spatial orientations. The belief “Rudy
Giuliani is famous” is true relative to some communities (e.g., the current community of New
Yorkers) but false relative to other communities (e.g., any community from the 18th century, the
current community of people in South Africa, any community of toddlers at a daycare center).
The belief “Three strikes is an out” is true relative to the rules of professional baseball but might
be false relative to a modified children’s game in which a child gets four strikes before he or she
is out. The belief “One should drive on the right” is true relative to the traffic laws in the USA
but false relative to the traffic laws in England. Note that these examples show that the things
that a belief might be relative to are diverse: people’s taste buds, geographical locations, spatial
orientations, communities, sets of rules, laws, etc.
30. A belief is SUBJECTIVE when its truth is relative to the believer in question. For instance, my
belief “Crème brûlée is the best dessert” is subjective because although the belief is true, it’s
only true relative to my taste buds. Thus, subjective beliefs are a special subclass of relative
beliefs: they are the relative beliefs whose relativity comes from a subject, the believer. One
must be quite careful here! My belief “Crème brûlée is the best dessert” is subjective but the
belief “Crème brûlée is the best dessert for Bryan” is not subjective but objective. Whether
crème brûlée is the best dessert is a subjective matter; whether it’s the best dessert for Bryan is
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objective: it’s an objective fact about Bryan that he finds crème brûlée to be the best—just like
it’s an objective fact about him that he has ten toes and knows a lot of baseball statistics.
Sometimes a belief is called ‘subjective’ outside of philosophical discourse when it’s thought
that no one knows whether the belief is true. But to avoid confusion I suggest that we reserve
‘belief that doesn’t amount to knowledge’ or ‘mere belief’ for such a belief, and let’s keep
‘subjective belief’ as explained above. In philosophy essays it’s almost always a bad idea to even
try using ‘subjective’!
You should make sure you fully understand each of (1)-(30), as they will be important for the midterm.
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