G.E Moore: Proof of an External World
The Proof
Moore believes that it is possible to prove that there is an external world, that is, a world that
exists independently of our experiences. If we can prove this, then we will have proven that
skepticism false, since being able to prove it shows that we know it.
Moore places three constraints on what constitutes a proof:
(i) The premises are different from the conclusion.
(ii) The conclusion follows from the premises.
(iii) We know the premises to be true.
The proof of an external world goes like this:
1. Here is one hand.
2. Here is another hand.
3. Hands are external things.
---------------------------------------------------------4. Therefore, there are external things (i.e., there is an external world).
Moore does not prove that he has hands. He takes that as a starting point. What he proves (or
tries to prove) is that there is an external world. Given that he as proven that there is an external
world, he can claim to know that skepticism is false.
Does his proof meet the three criteria?
Are the premises (1, 2, and 3) different from the conclusion (4)?
It seems so.
What about the other two criteria?
Does the conclusion follow from the premises?
Sure.
Do we know the premises to be true?
3 is true in the way that “If something is a bachelor, it is unmarried” is true. So, it is fair to say
that we know that 3 is true.
What is no so obvious is that we know 1 and 2 to be true.
Moore addresses two challenges to the suggestion that we do know 1 and 2 to be true.
Two objections Moore addresses
First objection
The first objection Moore considers is that we will not have a proof of an external world until we
have said—with respect to the premises—how any claim of the sort can be known at all.
Moore’s response is that he doesn’t think that it is possible to give such an account. But he thinks
this does not affect his argument against skepticism.
In some cases, Moore says, we can give an account. He claims that we could, e.g., give an
account of how to establish the truth of the belief that a certain hand is artificial and thus not a
genuine hand.
However, in many cases we cannot. We cannot, e.g., give a general criterion for establishing the
truth of the claim that we are not dreaming. You cannot inspect your experiences to find a mark
that distinguishes dreams from wakeful experiences.
But he doesn’t think our inability to do this implies that it is impossible to know that we are not
dreaming—because he doesn’t think that knowing requires a general criterion that says how it is
possible to know claims of the sort that show up as premises.
Moore proceeds by example. He says that he can give you an example of a belief that you can
identify as knowledge even though you have no way of testing it. The example is the belief that
you are awake right now and not dreaming.
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You have to be moved by the examples in order to find him persuasive.
We can thus see Moore as committing himself to the rejection of Methodism. This view says that
a belief cannot constitute knowledge unless there is a way to test it and it passes the test. That is,
Methodism says that unless you can specify the criteria for knowledge and show that the belief
satisfies the criteria, the belief is not knowledge.
In a nutshell, Moore defends Particularism—the view that we can know that a belief is
knowledge independently of any test or general criterion. Again, Moore argues by way of
particular examples of knowledge rather than general principles that define knowledge.
It is important not to misrepresent Moore. He is not saying that we never need evidence in order
to know. What he is saying is that at least some of our beliefs can be identified as knowledge
even though there is no way to test them.
By contrast, Descartes argues that a belief is not knowledge unless there is a test for it and it
passes the test—the test being whether you have established that it is impossible that your
evidence is deceiving you.
Second objection
The second objection says that even if proving an external world does not require you to provide
a test your beliefs must pass to be knowledge, you still have to prove those premises. The
objection is that Moore does not prove his premises, so his argument fails.
Moore denies that a successful proof has to have proven premises. I can prove my conclusion
even if I can’t prove my premises—because I can know that my premises are true even in the
absence of proof.
What is Moore up to here?
Descartes tries to respond to the skeptic by establishing certain basic knowledge and using that
knowledge to prove that he knows that he has hands and so forth, thereby proving the skeptic
wrong.
Moore rejects this traditional way of responding to the skeptic in that he does not try to prove
that he has hands. Instead, he takes knowledge of his hands as a starting point, from which it
simply follows that he knows that he is not in the Matrix (e.g.) and that skepticism is false.
We can see him arguing against the skeptic in the following way:
1. If I were in the Matrix, I would not know whether I had hands.
2. But I do know whether I have hands, so I know I am not in the Matrix.
3. And if I know that I am not in the Matrix, I know that skepticism is false.
4. So, I know that skepticism is false.
Why does Moore help himself to knowledge of his hands rather than proving it?
The answer is that he disagrees with the skeptic (and with Descartes) about what constitutes our
basic knowledge.
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The skeptic and Descartes take our basic evidence to be experience. But Moore thinks
that knowledge of objects and states of affairs in the external world constitute part of our
basic evidence.
Skepticism gets off the ground only if our basic knowledge—basic means not inferred from
anything—is restricted to our knowledge of our own minds. But, on Moore’s view, there is more
to our basic knowledge than knowledge of our minds—we know objects in the world just as
immediately as we know our own minds.
Beliefs about existence of hands, feet, beetles, etc. are just as foundational as our beliefs about
our own existence and our mental states, so, he thinks, we are entitled to the premises in the
proof of an external word and the proof we just saw to the effect that skepticism is false.
Final Thoughts
Notice that Moore can actually grant that in a way we do gain knowledge through our senses.
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He can grant that we need functioning eyes, ears, etc. in order to be aware of the objects,
because functioning sense organs are required for us to have experiences, so to this extent
we gain such knowledge through our senses.
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But he can, at the same time, maintain that the fact that functioning sense organs are
involved in our awareness of the objects does not imply that we make an inference from
our experiences to the existence of the objects. That is, he can say that we are directly
aware of our hands, of trees, of beetles, etc. Again, the awareness is direct in that we
don’t make an inference from our experiences to the existence of the objects.
This view is known as Direct Realism. Descartes, of course, is not a direct realist, because he
says that we know that we have hands by making an inference from facts about experience to
facts about the external world—whereas the direct realist says that no such inference is required.
We start with knowledge of the objects, just as we start with knowledge of our mental states.
The trouble with direct realism, one might argue, is that when we are challenged to say how we
know that we have hands, we say things like “I know because I see them.” The readiness of this
sort of response might suggest that it is the right response (or at least on the right track). But the
direct realist says that you should say something completely different—something to the effect
that you just know, i.e., that you know that you have hands non-inferentially (in the way that you
know that you have mental states).