<The following is a portion of Larrys Text, wikification is encouraged>
So what is truth? Here's a true claim: "2+2=4." Here's another: "Some dogs bark frequently." Here's another: "Mt. Everest is the tallest mountain on earth." Here's another: "Killing people for kicks is morally wrong." All of those sentences are meaningful and, moreover, true. So what do they have in common? What makes them all true claims, as opposed to false claims? That's the problem we're going to try to solve next.
Now I imagine that quite a few of you think that there is no such thing as truth, period. Whenever I say that a claim is true, what I really mean is that the claim is true for me. It may or may not be true for you. So when I say that it's true that ice is frozen water, what I really mean is that it's true for me that ice is frozen water. It's not true, period, that ice is frozen water. So we may define a kind of relativism, as follows:
Relativism about truth is the view that whether a claim is true or false depends in some way upon each individual person; so "P is true" is always short for "P is true for S (a person)."
I'm going to try to convince you that this view is not just incorrect, it's really obviously incorrect. And believe it or not, hardly any actual philosophers are relativists about truth; hardly any of them share this opinion that there is no such thing as truth, period. Almost all philosophers today think that there is truth, period. I imagine this is surprising to some of you -- you'd think that the relativism that pervades our society starts with philosophy professors and trickle down from there. But that's just not the case. Most philosophy professors aren't relativists about truth. So next I'll give you some objections to relativism about truth.
First objection. There are some rather obvious counterexamples to the view that the truth of a claim depends on an individual. Take, for example, the claim that ice is frozen water, or the claim that Mt. Everest is the tallest mountain in the world, or that 2+2=4, or that the world is more spherical than flat. Do you really want to maintain that whether those claims are true depends, in any way, on an individual? That just seems extremely implausible. I mean, why on earth would you believe that our attitudes makes any difference whatsoever to whether such claims are true? I mean, suppose a child thinks that ice isn't frozen water, but is a special kind of rock that is different from water. Would that make it true for the child that ice is a special kind of rock? I have a hard time seeing why anyone would want to say that. OK, so that's one reason not to accept relativism about truth.
Second objection. Relativism doesn't give any positive account of what truth is. It just says that whatever truth is, it depends on individuals. So what is it that depends on individuals? Truth. Right: so what is truth? The point then is that even if truth is relative, you've still got to say what it is that is supposed to be relative. Saying that truth is relative doesn't tell us what truth is. Now, this is an objection to relativism only if you take relativism to be a theory about what truth is. So far, this objection just raises a question.
In my experience with undergraduates and others who espouse relativism, there does seem to be a theory of what truth is that goes along with relativism. The theory is basically the following:
P is true for S iff S believes that P.
So "Ice is frozen water" is true for me if, and only if, I believe that ice is frozen water. Basically then, truth is belief. So remember my definition of "relativism about truth"; it was "the view that whether a claim is true or false depends in some way upon each individual person." We might ask: how does the truth of a claim depend on each individual person? The above definition of "truth" explains it: the truth of a claim depends on whether an individual believes it. If I believe the claim, it's true for me; if I disbelieve it, then it's false for me; if I haven't made up my mind, then the claim is neither true nor false for me.
That leads us to the second objection: namely, that it is extremely implausible that the concepts of belief and of truth are the same. I can point out all sorts of differences that make it very clear that the concepts of belief and truth are different. For one thing, if belief and truth are the same, then why do we have two different words for the same thing? Why don't we just always talk about belief, or always about truth? And why do we often talk as though they're different -- as though there are such things as false beliefs, and truths that haven't been discovered yet? If belief and truth are the same, then everything I believe is true for me; do we really want to say that?
That seems like it would be far too easy for me to achieve truth; all I have to do is believe something, and voila, I have the truth! No need to do experiments or give arguments to prove that a claim is true; just believe it and that makes the claim true! Honestly, what's the point of arguing about things if belief and truth are the same? An argument is supposed to show that its conclusion is true. But if truth is just the same as belief, then why do I need to go to the trouble of giving an argument? My believing a claim is enough to make it true. I don't have to argue that God exists, because if I believe that God exists, then it's just automatically true (for me) that God exists.
Third objection. To explain the third objection, I am going to have to advance two principles, which I and most other philosophers think are obviously correct. So here are two principles:
(1) If it is true that P, then P.
(2) It is never the case both that P and not-P.
To illustrate: if it is true that snow is white, then snow is white. And it is never the case both that some snow is white and that some (the same) snow is not white. The second principle is called the Law of Noncontradiction. It basically says that there aren't contradictions in the universe. It can't be the case that 2+2=4 and that 2+2_4. Direct contradictions can't both be true.
The third objection states, then, that relativism about truth violates these two principles. Let's say that Billy Bob, who hasn't ever been away from his corner of California, believes that Mt. Shasta is the tallest mountain in the world. Then by the relativist definition of "truth," it's true for Billy Bob that Mt. Shasta is the tallest mountain in the world. Right? Because all he has to do is believe it, and then it's true for him. Well then, according to the first principle, it follows that Mt. Shasta is the tallest mountain in the world. But then of course I disagree with Billy Bob, because I believe that Mt. Shasta is not the tallest mountain in the world. So then it's true for me that Mt. Shasta is not the tallest; and it follows by the first principle that Mt. Shasta is not the tallest mountain in the world. Therefore, Mt. Shasta is the tallest mountain in the world and it is not; which is impossible, according to our second principle. It is never the case both that P (Mt. Shasta is tallest) and that not-P (Mt. Shasta is not tallest).
In general, the problem is that people disagree about all sorts of different things. But then the relativist would be saying that totally contradictory propositions can be true for different people at the same time. But according to the first principle, that means that the world itself is in totally contradictory states at once, which is absurd. People may disagree, but the world is only one way or the other. You can disagree about it all you like; the world doesn't care. So if you disagree with me, and you claim that P, and I claim that not-P, and P is a precisely-worded sentence, then only of us can be right.
Well, that's all I'm going to say against relativism about truth. I am going to talk now as though truth is not relative to individuals; whether a claim is true or not, we'll say from here on out, depends not on you or me but on the how the world is. It's only the world that makes sentences true -- not our beliefs about the world.
Now at this point I think some of you might be wondering: well, if truth isn't relative to individuals, and truth is different from belief, then how can we really know whether or not a claim is true? If truth is independent of us, and depends only on the world, then how can we know what is true? I'm not going to answer that question now, because it's off-topic. You might be asking: How can we know what is true? But the question we have set for ourselves is, instead: What is truth itself?
Do you see the difference? On the one hand, you can ask how we can know whether a claim is true; on the other hand, you can ask what it means to say that the claim is true. Consider these two propositions:
(1) I know that the sentence, "Mt. Everest is the tallest mountain in the world," is true.
(2) The sentence, "Mt. Everest is the tallest mountain in the world," is true.
Those are two different propositions. The first one is a claim about me, about what I know. The second is a claim about a sentence (that the sentence is true). So what we're concerned with now is truth, not knowledge. Truth is different from knowledge, just as it is different from belief. You can see that just by considering the fact that a claim can be true even though I don't know it, and even though I don't believe it; whether I believe or know it, or not, it can still be true.
Before we get into some positive theories of truth, I want to quickly introduce one bit of terminology. Propositions are what sentences are supposed to express. So the sentence "Snow is white" is supposed to express the proposition that snow is white. And the proposition that snow is white is supposed to be different from the sentence, "Snow is white." Which makes some sense, if you think about it: we have different ways of saying that snow is white, right? Not just the sentence, "Snow is white." For example, I could say, in German, "Schnee ist weiss," or in French, "La neige est blanche." Both of those sentences express the same proposition as "Snow is white."
Why am I introducing this term "proposition"? Well, some philosophers insist that only propositions can be, properly speaking, true or false; sentences are not true or false, properly speaking. It's the thing that a sentence says, the proposition that the sentence is making, that is either true or false -- that's the idea. Anyway, I'm going to put theories of truth in terms of propositions, as you'll see.