The foundations of knowledge
According to all foundationalist epistemologies,
a) we need to find some class of beliefs, of which we have secure knowledge; and
b) once we find this class, we can then honor some of our other beliefs with the special status of knowledge by showing that they are properly supported by the members of this class of foundational beliefs.
So every foundationalist epistemology needs to answer two main questions:
a) the nature of the foundations: what are the foundational beliefs? and
b) the nature of the justification: how do the foundational beliefs support the other, derivative, beliefs?
If we could find the right foundational beliefs and the right explanation of how they support other beliefs, then we might be able to find a way around Marie, the unscrupulous scientist, and Descartes' demon.
With the right answers to these two questions, we might be able to deal with the problems created by the fact that the evidence of experience is always defeasible. The possibility is worth investigating.I said just now that foundationalism has appealed to many empiricists. But it is a natural view for any rationalist as well. Rationalists believe that reasoning is the best source of knowledge; and, in the most rigorous sort of reasoning—namely, mathematical proof—we start with axioms, as our foundation, and proceed by logical steps to our conclusions.
The axioms are certain: they are the foundations. And they support the consequences we draw in the strongest possible way: indefeasibly.Descartes is typical of rationalists in this respect. For him, the foundational class was just the class of thoughts that could not be doubted, because you had indefeasible evidence for them. His famous slogan “I think, therefore I am” was one thing he thought you couldn't doubt. You couldn't doubt it because you couldn't be fooled about it. Even someone as clever as Marie, our unscrupulous scientist, couldn't be fooling the brain if she got it to think that it was thinking; and if it thought that, it would know it existed, because you can't think without existing.
It is worth noticing that there are many arguments of the form of the cogito that are equally valid. For example, “I laugh, therefore I am.” It's true that you can't think if you don't exist, but you can't laugh unless you exist either. What is special about the cogito is that the premise—”I think”—is something that is not just true whenever I think it but also indubitable or certain, according to Descartes, whenever I think it. “I laugh,” on the other hand, could be believed by someone who wasn't laughing (for example, by Albert in the vat). The reason Descartes wanted a premise that was indubitable was that he wanted to use the foundationalist strategy. He wanted a premise that was certain (“I think”) from which to deduce his conclusion (“I exist”) because he thought that a valid argument that has premises that are certain can transmit the certainty to the conclusion. (We'll learn more about valid arguments in the next chapter.)
But, as we have seen, Descartes' foundational class was too small to provide us with a basis for knowledge of the physical world. For there is nothing at all—save our own minds—whose existence is certain. Since Descartes required that all knowledge should be certain, that led to the general attitude of doubt that is the most extreme form of skepticism about the physical world.
For Locke, on the other hand, the foundational class of beliefs, from which we derive our knowledge of the physical world, is the class of perceptual beliefs.
Locke was, therefore, an exponent of a form of empiricist, foundationalist epistemology in which our beliefs about the world all have to be supported by sensory experience, just as our beliefs about our minds have to be supported by reflection. That was Locke's view of the nature of the foundations.Locke was aware of Descartes' arguments and of the skepticism about the physical world to which they so easily lead. But he had an answer for them, which relies on two main claims:
a) Our experiences are involuntary. We cannot simply choose what experiences we should have. I can decide whether or not to open my eyes. But I cannot choose whether I will see this book in front of me once I do open my eyes. So something other than my own mind must cause my experiences.
b) Our experiences are consistent: “Our senses in many cases bear witness to the truth of each other's report.” For example, we can check on what our eyes tell us when we see a fire by using our hands to feel its warmth.
These are, indeed, arguments that might satisfy someone who was worried about whether some particular experiences were in fact reliable. If I was unsure whether a vision in the desert was a mirage, for example, it would help to check whether my other senses confirmed it. I might run to where the water seemed to be, to find out if I could touch or taste it. Similarly, it seems reasonable to think that if I could make an experience come and go simply by wishing, then that experience could not be evidence for the existence of a physical object. But notice that neither of these points really meets the skeptic's worry. For Albert, the brain in the vat, could think both (a) that his experiences were involuntary and (b) that his experiences were consistent; but he would still be wrong if he believed his senses.
And the demon would make Descartes' experiences both consistent and involuntary too—or at least as consistent and involuntary as they actually are.The problem is that though the involuntary nature of my experience may show that it must have some cause outside of my conscious mind, the story that I am a brain in a vat seems to account for the involuntary nature of my experience just as well as the story that I am experiencing a real world. And though the consistency of our experience does need explaining, it seems as if the story that I am a brain in a vat just could be the right explanation. It seems that to say our experience is only defeasible evidence for the existence of things in the world is just to admit that the suggestion that all our experience is faked is a real possibility. If that is right, whatever reason we give for trusting our senses cannot rule out the possibility that they are misleading us. Someone who believes that we have no right to think that any of our beliefs about the world could not be wrong is called a fallibilist.
Locke followed this line of argument, and so he said that our senses provide us with grounds for probable beliefs, not for certain ones. But then he claimed that probability is all that we practically require.
He that in the ordinary affairs of life, would admit of nothing but direct
plain demonstration, would be sure of nothing in this world, but of perishing quickly.
Certainty comes only with those truths of reason that we can establish by “direct plain demonstration.” If you will accept only these truths and refuse to believe the evidence of your senses, Locke is saying, you will simply end up suffering the consequences. Skepticism may seem a real possibility in the study, but no one could survive as a skeptic in the real world.
Locke's definition of knowledge is closer than Descartes' to the one we normally assume, in the sense that he agrees with many of our commonsensical claims to know things.
He allows, for example, that we know that we have hands, because we have consistent evidence from our experience that we have hands. We began our search for a definition of knowledge in the hope that we could answer the question whether—and if so, how—we know that we aren't just brains in fluid. Locke's answer has to be that we do know this. For, as we saw, the PDJ means that if we believe something and it is a logical consequence of something we know, then we know it too. And since it is a logical consequence of my knowledge that I am experiencing my two hands that my experience is not being faked by Marie, I must know that I am not a brain in Marie's vat.As for Locke's explanation of why the brain in a vat does not know things about the physical world, it must be that the brain's beliefs are false, not that they are unjustified. For it is evidence that justifies beliefs, and a brain in a vat would have exactly the same evidence that its senses were not deceiving it as I now have that mine are not deceiving me. It follows that the brain is as justified in its beliefs as it would be if they were true, as mine are.
Here is the problem with this explanation of why Albert's brain does not know things about the world. Suppose Marie allowed Albert's brain to have some true beliefs. Suppose she made him believe that the sun was shining on a day when it really was shining. Suppose she got him to believe it by giving him just the evidence I now have that the sun is shining (which in my case is produced by looking out of my window on this sunny day). Needless to say, Albert wouldn't know that the sun was shining. Yet Locke would have to say that he did know it, since the brain would have a justified true belief. (After all, Albert's belief is justified if mine is: we have the same evidence.) Descartes' view of knowledge—which required indefeasible evidence—led to skepticism. He had to deny that we knew anything about the physical world. So his theory led to the conclusion that we do not know some things that we do know. But if we simply weaken Descartes' justification condition to allow defeasible evidence, we get Locke's theory—which leads to the conclusion that the brain knows things that it doesn't know. If knowledge is justified true belief, skepticism is not so easily evaded.
2.6