First, try not to conflate theism with Christianity (and faith). Various theistic traditions have forms of natural theology that do not include the notions of revelation and faith. Theism is much broader than Christianity.
What is faith? I will tell you what I think it is, but you must also tell me what you think it is if I am to understand where you are coming from. I would say that (divine) faith is belief based on God's word (or revelation). Suppose I am living in Rome in 1453 and God reveals to me that the Ottomans have taken Constantinople. I don't believe this because I have seen it, I believe it because I have accepted and trusted the word of another, namely God. A few weeks later a messenger arrives from the Eastern Empire and relays the information that Constantinople has fallen. Now I have two reasons to believe: divine faith and natural faith: the word of God and the word of man. Suppose I travel to the Hagia Sophia in 1454 and see for myself that the Ottomans occupy Constantinople. Now I have three reasons. The third reason is not faith-based.
What do you think faith is? And what are some examples of faith-based propositions?
I see that you were upbraided for misrepresenting Thomas Aquinas earlier in the thread. In
ST IIae IIae, Q. 2, A. 1 he addresses the nature of the act of faith. Perhaps Aquinas would say that faith is a kind of knowledge, but he certainly distinguishes it from the sort of knowledge we gain by first-hand sight.