Epistemologists talk about various different epistemic features of belief. Or at least, they use different words to describe a group of closely-related features of belief. These include "justification," "warrant," "rationality," "probability," and others. Iím not going to try to explain the differences in meaning between these terms; the differences arenít as important as the similarities. Anyway, of these four terms, the term that has been most widely used and discussed, the word that has been bandied about the most, in the past twenty years or so anyway, has been justification. And as you might have guessed, there is something called the theory of justification, the main question of which is: "What is justification?" or "When is a belief justified, and when not?"
So letís focus on justification. And let me begin by saying a few very general things about justification. We can say that more than just beliefs are justified; actions, emotions, laws, theories, and so forth, a whole panoply of things can be justified or not. But in epistemology itís mainly beliefs that are said to be justified or not. So the topic is not best stated as "justification," period, but as justified belief. And the question is: "When is a belief justified, and when not?" Or if you want to put it in terms of meaning, you could ask: "What does the term, Ďjustified beliefí, mean?
Thereís something more that I can say to give you a better fix on what Iím talking about. A justified belief is one that we are within our rights in holding. What sort of rights? Not political rights, of course; not even moral rights; maybe something like "intellectual" rights. The idea is that we want to be responsible believers. We donít want to just go off and believe anything, with total irresponsibility. In some sense, itís bad just to believe whatever pops into mind. So you have some sort of responsibility, an intellectual responsibility, an intellectual obligation to yourself, to believe what is true and to avoid believing whatís false. If youíre being intellectually responsible, then youíre within your intellectual rights in believing something; and then youíre justified in your belief.
So itís often said that justification is a normative notion. That means that it has to do with norms, rights, responsibilities, obligations, and so forth; or more generally, we could say (hereís a rough definition):
A concept is normative iff it is a concept regarding or depending on the norms, or obligations and permissions (very broadly construed), involved in human conduct.
The concept of justification is definitely normative in this sense, because it is a concept regarding the norms of belief.
So you know two things, at least, about justification so far: first, justification is an epistemic feature of beliefs, meaning that it aims at the truth, as it were; and second, the concept of justification is a normative concept, because it is a concept about norms of belief.
Hereís a third general feature of justified belief: If a belief is justified, there is something which justifies it. So letís call whatever it is that justifies a belief the justifier of the belief. So the claim is: If a belief is justified, then it has at least one justifier. Now, notice first that I havenít said anything about what sort of thing a justifier can be. More about that in a bit. But an example of a justifier would be some evidence that I accept; if I accept some evidence, then that evidence might be a justifier of my belief. For example, if I am aware of the bloody footprints, blood in O. J.ís Bronco, DNA confirmation, and so forth, all of that can be evidence for my belief that O. J. Simpson is a murderer. In that case, the justifiers are all that blood evidence, or rather my acceptance of that evidence; the belief that is justified is my belief that O. J. is a murderer.
But not all justifiers would have to be what can properly be called "evidence"; there might be some totally different kind of justifiers out there. But to be justified, a belief has to have a justifier.
So far, Iíve just been reciting some general features of justification that pretty much everyone agrees on. But now weíre approaching the point where people disagree. Because what people disagree about is what the justifiers are. In other words, the following question is the main bone of contention: What sorts of things are justifiers? There are, to simplify, three answers -- three different views about what sorts of things can be justifiers:
(1) Beliefs only.
(2) Beliefs together with other conscious mental states.
(3) Beliefs, conscious mental states, and other facts about us and our environment (which we may not have access to).
Iím not going to give you examples of each of these three kinds of justifiers; Iíll save the examples for the theories of justification that Iím about to explain to you. Right now all I want you to see is that there are those three different views about what sorts of things that justifiers can be.
But at least sometimes, the justifier of a belief is another belief. When, for example, I believe that O. J. is a murderer, I base that belief on other beliefs -- namely, about the blood evidence and other evidence. Strictly speaking, my belief isnít based on the evidence itself -- after all, what if I didnít believe it? What if I thought that all of that evidence were just a hoax? For that matter, what if the evidence existed, but I didnít know about it? Then of course, my belief that O. J. is a murderer wouldnít be based on that evidence, just because I didnít know it was there at all; or, if I thought the evidence were a hoax, then surely my belief couldnít be based on that evidence. So here is my point: when my belief is based on evidence, actually what my belief is based on is another belief, namely, a belief or beliefs about the evidence.
For convenience and brevity, let me use letters, Pís and Qís, to stand for beliefs. So the idea weíre considering now is that a belief, Q, can be justified by another belief, P. So P justifies Q. Now I want you to consider a possibility -- see what you think of this. Suppose that P -- the justifier -- is itself, not justified at all. Suppose itís just totally arbitrary. I picked the belief out of a hat; I got it from a fortune cookie. Then would it be possible for P to justify Q? Surely not.
Let me give you an example. Suppose I believe that there is intelligent life on Mars, and I base this belief on a further belief, that there is a feature on the surface of Mars that looks like a face, and that this face could only have been made by intelligent life. So the justifying belief is: That face-like feature on Mars could only have been made by intelligent life. And the justified belief is: There is intelligent life on Mars. But suppose further (something that really is the case) that the justifying belief is itself totally unjustified. I am in no way in my intellectual rights if I suppose that this face-like feature on Mars could have only been made by intelligent life; that view of mine is totally irresponsible, intellectually speaking. Would my belief that there is intelligent life on Mars be justified then? It has a justifier, doesnít it? Yes. But the justifier is itself not justified. So definitely belief in life on Mars is unjustified; if itís going to be justified, it has to be justified by some belief which is itself justified. If the justifying belief isnít itself justified, then it canít do any justify anything else, no matter how much I might want it to.
So I think we can accept a general rule:
If a belief, Q, is justified by another belief, P, then P must itself be justified.
If P isnít justified, then it sure canít justify Q. The only way that P could justify Q is if P is itself first justified.