Two Questions about Truth

What is it for a claim to be true?

Here is the standard common sense answer:  There is a world out there independent of our minds and it is some specific way (by “world” philosophers mean all of existence, including the entire universe and many would include all of the past and the future as well). To say that the world is some specific way is to say that consists of things have some properties while lacking others and things standing in some relations to other things, but not other relations.  For a sentence to be true is just for what it expresses to “fit” or “correspond” to the way the world is.  To take a simple case, the claim “the bird is on the wire” has a meaning we all grasp.  It represents the world as containing a couple of things, the bird and the wire, and for these things to stand in a certain relation, the on relation.  If those things out there in the world stand the specified relation, then the sentence is true.  Otherwise not.  This is known as the Correspondence Theory of Truth. 

How do we know that a claim is true?

I don’t know.  Tell me what sort of claim you have in mind and then we can look to the appropriate branch of science or philosophy and talk about its methods.  But that’s a different class (take PHIL 160 Philosophy of Science).  So I’m not going to answer this question here.  The important thing to notice about this question here is how it is different from the question we considered above.  Specifically, it’s a question about knowledge.  Implicit in this may be questions about justification or well supported belief.  These relations involve more than the relation of correspondence between the world and the content of a sentence. Knowledge and justification involve some person’s mind as well as the content of a sentence and the way the world is.

See the rationality pages for more on truth.