Tautology and Logical Necessity

It's been awhile since I did a post that was on the topic of logic and philosophy as such. Recently an on-line conversation reminded me that I have fonder view of tautology than many people. (If you know what tautology is but don't care, you might rather skip this post. If you're willing to follow along for the ride, it helps to muster some interest in logical proofs and how they work.)

Tautology is something that is self-referencing, and so basically true by definition. Consider the sentence "An apple is an apple" or the more generalized and over-used "It is what it is." A tautology is something so self-referencing that it couldn't possibly be false. You can fault it for being dull or obvious, but not for being false.

Tying in another thread: There is an argument for the existence of God that starts by arguing whether God is necessary or contingent. That argument itself isn't the point here; it's used as a touchstone to bring up the distinction about whether a thing is necessarily true or just happens to be true (but might have been otherwise). So I mean necessarily true in a more technical sense that "It's necessary for it to be true", like the fact that A equals A, or "It is what it is." Those things are necessarily true; they couldn't be anything else. (Still awake?)

Anything that is necessarily true is, ultimately, a tautology. That is: if we have our definitions right, if someone wants to prove that a thing is necessarily true, then they must prove that their point is inherent in the nature of the things being discussed: that once all the variables are reduced, what is left is a tautology. If a thing cannot be reduced to a tautology -- if it doesn't rest on the definitions of the things and the nature of the topic -- then it is not necessarily true. It may happen to be true but that's contingent or circumstantial. So even the most complex thing that can be proven to be true must rest on the nature of the reality beneath it. Anything else is chance.

Tautology has an evil twin, the circular argument. We can tell them apart: while tautology argues that A = A, the circular argument asserts that A = B and proves it by the assertion that B = A; each is used to prove the other. When a circular argument is reduced, there's nothing left. When a tautology is reduced, you still have what you started with, but maybe it's better understood.