Aquinas’ via negativa is well-known. We cannot say what God is, only what he is not. Aquinas is also notorious for his Five Ways. Aquinas seeks to prove the existence of God, claims to have done so, yet also says that God’s nature cannot be known. This seems to be mistaken, however. If one claims to have knowledge that a being or thing exists, then it necessarily follows that one must also have at least some knowledge about that being or thing’s essence. If you claim that X exists, you must have at least some concept of what X is, otherwise you could not claim that X exists, since knowledge of X’s existence includes a minimum amount of knowledge about what X is. One might say that this is only true for things in the universe (contingent), and that God is an exception (necessary), yet this only makes God even more estranged from the universe, making it seem that a deist belief is as far as one can go before stretching beyond the realms of evidence or logic.
For the past century or so, the question of religious language has caused numerous problems, the biggest being whether talking of God is meaningful or meaningless.
Thomas Aquinas established the via negativa, a way of talking about God which aims not to say what God is, but what God is not. Moreover, the use of analogy is for Aquinas a way of talking about God. He uses the example of a bull to explain analogy of attribution. An expert can tell the health of a bull from its urine, but the health of the bull is not in the urine as such, and is just a reflection of the actual health of the bull. Likewise, the world is a reflection of God, and a reflection of his goodness (problems obviously arise here). The language of symbol is a way of explaining things that cannot otherwise be explained because of their nature as experienced (William James would describe them as ineffable). However, the use of religious language does not seem to get very far, particularly with skeptics or atheists, seeming helpful only to those who believe already.
A.J. Ayer used the verification principle to do away with all religious and moral statements as mere noise and nothing else. The verification principle states that ‘a proposition is only cognitively meaningful if it can be definitively and conclusively determined to be either true or false (i.e. verifiable or falsifiable).’ Moral statements are for Ayer nothing more than an expression of approval or disapproval of something, but add nothing factually to a statement (his theory is known as the ‘boo-hurrah’ theory). Since religious statements cannot be verified, Ayer claims that they are ‘evidently nonsense’.
Ludwig Wittgenstein believed that language is that of a game, and that when we speak we are partaking in a language game. We play many different language games, he argued, with many different people and in many different places. Outside a language game, the language is meaningless, but inside it is meaningful (which begs the questions whether language games is all there is, and if this is so, whether objectively all language is just primitive noise, though Wittgenstein probably would not agree with this). Religious language is another language game, but does that mean that if you are not playing the game the language is meaningless? Perhaps so.
Speaking of God is difficult, regardless of one’s belief. It remains unclear as to the meaning of religious language, and whether it holds any weight at all.