It may sound odd to wonder how and why truth matters — under most circumstances the importance of truth should be obvious. Nevertheless, the question of truth does have problems which are difficult to address; among them is the question of what role the notion of “truth” plays in our philosophy and our understanding of the world around us.
The simplest and most obvious definition of truth is, without a doubt, that which accords with reality. Here, we can say that truth matters because reality matters. As simple as this is, it is also begging a very important question: just how do we tell what accords with reality and what doesn’t? This is a much more difficult question to answer, one which occupies a great deal of time an attention.
Because of difficulty, an important task of epistemology, closely related to defining and explaining truth, is to develop criteria of truth which allow us to reliably and consistently distinguish true from false claims. We are constantly bombarded from all sides by wildly divergent assertions, many of which are mutually incompatible. How do we know which to accept, which to reject, and which merit closer attention and study?
Of course, not everyone quite agrees that “truth” is best defined and understood simply as correspondence with reality. That certainly isn’t how everyone uses the term even in normal conversations — and it must be acknowledged that many definitions of truth are derived from a person’s philosophical system. For example, empiricists will define truth one way while existentialists will define it another way.
How a person conceives of truth will, of course, have a profound influence upon what sorts of criteria they use of differentiating between truth and falsehood. A person who adopts the Correspondence Theory of truth will use one set of criteria while someone who adopts the Semantic Theory of truth will employ different criteria; as a consequence, they could easily look at the exact same claim and reach different conclusions about its truth status.
Thus, another fundamental problem which needs to be looked at when discussing truth is: whenever someone claims that some idea is true, what exactly do they mean by “true”? And what does it mean if we say that it isn’t true? They might not mean the same things you mean! It would be difficult to disagree with a person over the truth of a claim if we aren’t speaking the same “language” of truth in the first place.
If we define truth differently and use different criteria of truth, then it would be easy to disagree about what is and is not true, but very difficult to reach some sort of common ground. It isn’t unusual for people to employ very different ideas about truth unconsciously, so one of the tasks of epistemology is to develop clear and forthright explanations of the nature of truth which people can discuss out in the open, perhaps even reaching some sort of accord.
Thus, it makes a lot of sense to have a clearer understanding about how you and others understand and define truth before disagreeing too strenuously about just what qualifies as true in the first place. That could prevent any number of unnecessary misunderstandings before they go too far.
