The truth contained in reliabilism is, however, concealed by an error. What a person originally believes as a result of prejudice may later be accepted on the basis of
scientific evidence. Therefore, the reliabilist must be in error when he claims that it is what originates a
-168-belief that converts it into a justified -168-belief and knowledge. This is, in effect, to confuse the reason a person has for believing something with the cause of his believing it. The confusion is such a common one that we might name it the causal fallacy.
It is easy to see how the fallacy arises. When a person's justification for her belief is based on evidence, then she believes what she does because of the evidence. This suggests a causal account of what is involved when the justification of a belief is based on evidence. it suggests that the notion of a justification being based on evidence should be explicated in causal terms. Following this proposal, a person's justification for her belief is based on certain evidence if and only if her belief is causally related in some specified way to the evidence. How to specify the exact way in which the belief must be causally related to the evidence would remain a problem on this approach, but it would be a problem of detail rather than of principle. All such theories must be rejected, however.
Often the evidence on which a justification is based does causally explain the existence of the belief, and it may even be admitted that sometimes the belief is justified
because of the way in which it is causally explained by the evidence. Nevertheless, it is also possible for a justified belief to be causally independent of the evidence that justifies it. Indeed, it may well be that the evidence in no way explains why the person holds the belief, even though her justification for the belief is based on the evidence.
The evidence that justifies a person's belief may be evidence she acquired because she already held the belief, rather than the other way round. This is to be expected, since it is commonsense to distinguish between the reasons that justify a belief and the causes that produce it. The causes of belief are various, and, though the reasons we have for a belief sometimes cause the belief to arise, the belief may also arise from some other cause than having the reasons that justify it. Having the reasons we do may justify the belief, however, even though they have no causal influence upon the belief at all.
An example will illustrate. It is easy to imagine the case of someone who comes to believe something for the wrong reason and, consequently, cannot be said to be
justified in his belief, but who, as a result of his belief, uncovers some evidence which
completely justifies his belief. Suppose that a man, Mr. Raco, is racially prejudiced and, as a result, believes that the members of some race are susceptible to some disease to which members of his race are not susceptible. This belief, we may
imagine, is an unshakable conviction. It is so strong a conviction that no evidence to the contrary would weaken his prejudiced conviction, and no evidence in favor would strengthen it. Now imagine that Mr. Raco becomes a doctor and begins to study the disease in question. Imagine that he reads all that is known about the disease and discovers
-169-that the evidence, which is quite conclusive, confirms his conviction. The scientific evidence shows that only members of the race in question are susceptible to the
disease. We may imagine as well that Mr. Raco has become a medical expert perfectly capable of understanding the canons of scientific evidence, though, unfortunately, he becomes no less prejudiced as a result of this. Nevertheless, he understands and
appreciates the evidence as well as any medical expert and, as a result, has reason for his belief that justifies it. He has discovered that his conviction is confirmed by the scientific evidence. He knows that only members of the other race are susceptible to the disease in question. Yet, the reasons that justify him in this belief do not causally explain the belief. The belief is the result of prejudice, not reason, but it is confirmed by reason which provides the justification for the belief. Prejudice gives Mr. Raco conviction, but reason gives him justification.
Harman and others, most notably Marshall Swain and Alvin Goldman, have suggested that a belief is based on evidence only if the evidence conditionally or partially explains the belief. 21 The idea is that, even if the belief is not originated by the evidence on which it is based, it must be causally sustained by the evidence. Again, in the typical case, this will be true. Usually, the reasons a person has for a belief can be expected to have some causal influence on the belief, even if they do not originate that belief.
It is, unfortunately, difficult to evaluate the claim that the reasons that justify a belief must always partially explain or causally sustain the belief because a sufficiently
precise account of partial explanation and causal sustenance is lacking. There appears to be no better reason for supposing that the evidence that justifies a belief must partially explain or causally sustain the belief than for supposing that it must originate it. The explanation for this is that we may suppose that the evidence justifying Mr.
Raco's beliefs does not in any way explain or causally sustain his belief. What explains and sustains his belief is his prejudice. His belief is neither strengthened nor explained by his discovering the evidence for it. His prejudice gives him the strongest level of conviction, and the evidence adds nothing to the strength of it.
One might, however, suggest that his conviction is conditionally or counterfactually explained or sustained by the evidence, nonetheless. It might be proposed that if Mr.
Raco were not to believe what he does out of prejudice, he would believe it as a result of the evidence. This is again likely, but it need not be so. Imagine that Mr. Raco is so dependent on his prejudice that if he were to cease to believe what he does out of prejudice, he would become quite mad and become uninfluenced by reason. To avoid such an objection one might propose, as Swain did, that to say the belief is sustained by the evidence is only
-170-to say that if Mr. Raco were not -170-to believe what he does out of prejudice but were -170-to continue to believe it nonetheless, then he would believe it as a result of the evidence.
Perhaps this is to be expected, but must it be so? Again suppose that were Mr. Raco to cease to believe what he does out of prejudice, he would become quite mad and uninfluenced by reason; then were he to believe the same thing though not out of prejudice, he would believe it as a result of madness.
The point is the one with which we began. Though evidence ordinarily has some
influence over belief or would have if other factors were to lose their influence, this is really incidental to justification. The analogy between justification and validity explains why. If a person validly deduces a conclusion from something he knows, this may cause him to believe the conclusion or influence his belief in the conclusion. But the validity of the inference does not depend on this causal influence. If valid deduction had no influence whatever on whether a person believed the conclusion, that would not undermine the validity of the inference. Similarly, if someone justifies some conclusion on the basis of something he knows, this may cause him to believe the conclusion or influence his belief in the conclusion. The justification of his conclusion, however, does not depend on the causal influence. Thus, a person may justify a
second belief in terms of a first belief and the justification of the second belief may be based on the first without the second belief being causally influenced thereby.
The preceding discussion rests on a distinction between explaining why a person believes something, on the one hand, and explaining how he knows it, on the other.
When a person knows that his belief is true, the explanation of why he believes what he does may have something to do with his having the evidence he does, but it need not. The explanation may rest on political, erotic, or other extraneous influences, but the explanation of how a person knows that his belief is true, when the justification of the belief is based on evidence, must be in terms of the evidence. It is how a person knows that is explained by evidence. Why he believes what he does may be explained by anything whatever. Therefore, a justification of a belief that is known to be true is based on certain evidence if and only if his having that evidence explains how he knows that the belief is true. The evidence explains how the person knows, moreover, if and only if the evidence justifies the person's belief. The manner in which evidence justifies a belief is explained in the account of complete justification in the last
chapter. Evidence that justifies a belief consists of that part of the acceptance system of a person which yields complete justification.
The idea of evidence explaining how a person knows may be further clarified by recalling once again that our primary concern is to provide
-171-a theory to expl-171-ain how people know th-171-at the inform-171-ation th-171-at they possess is correct.
If the evidence that a person has justifies her belief that p, then the evidence explains how she knows that the information that p is correct. She knows this from the
evidence. Similarly, if a person is asked how she knows that p, her reply will be to justify the claim that p in terms of her evidence. It is appeal to her evidence that
shows that she knows and how she knows. Thus, a justification based on evidence explains how a person knows that p if that justification would be a correct answer to the question 'How do you know that p?'