You haven't quite got that right, Viktor. True belief in God is not an act of faith. Faith implies an acceptance of a thing based on pure trust alone. "Faith" is also used to describe what "persuasion" a person is (Catholic, Baptist, etc.). I suppose there are a lot of people out there that accept many things purely on trust but God should not be one of them! Anyone with a deep conviction about God will tell you that it is based on some inner, personal experience. They have seen and felt something communicated to them that is undeniable, unshakable, profound. They may tell you it was the most "real" experience of their life leaving a lasting impression decades later.
Atheists are totally closed, simply deny the possibility of God outright. Not only for themselves but all others. They will tell you he is neither "necessary" nor scientifically valid. Many people also wrongly assume that "faith" in god is contrary to science. That is wrong too. Believing in God has absolutely nothing to do with one's education or ability to pursue science! Albert Einstein was a deep believer in God. But denial of the possibility of god because you simply haven't seen it for yourself is utter foolishness since you cannot prove a negative. Do you disbelieve in black holes, quarks or gamma rays because you haven't seen those either? They refuse to admit that their "faith" is simply a human-centric rather than a god-centric one. An impersonal philosophy vs. a personal one. They prefer to think that consciousness, self-awareness and intelligence came from dust rather than from a greater consciousness and awareness. They say they see no evidence for God. I can at least understand that as that is where I stood when young until something changed and I had the experience of a lifetime.
Agnostics remain open looking for proof. Again, pure foolhardiness to expect someone else to hand it to you. It is like they expect a miracle to appear before them or some concrete evidence handed them! Why would anyone expect concrete evidence for something which by its very nature is NOT concrete, not material, ie, spiritual? No one may prove to another God's existence or not. That is simply not something we may show or "prove" to another person. Each person must go by whatever belief they hold until the time comes for them to advance to something better at whatever rate and time best suits them.
I disagree. The empirical and rational evidence for God's existence is readily apparent, but atheists are just flatout irrational for all their guff to the contrary. Either the universe in some form or another has always existed (the absurdity of an infinite regress of contingent causality), it came into existence from nonexistence (an absurdity of ontological order) or the eternal ground of existence is immaterial, and only an immaterial entity of personhood could possibly freely elect to cause the existence of the material entity of time. The effect of a mechanical cause would axiomatically be given from eternity, would necessarily be material, which leads right back to the first absurdity. Hence, God must be. The first two options are sheer madness. Atheism is madness. Faith in God's existence is firmly based on reason, and the deeper, spiritual faith of conviction or trust in the true God follows. Obviously, the latter kind of faith entails direct revelation from God, but I assure you as one who has thought it all through, there exists ample logical reasons that lead directly to the God of the Bible as opposed to the others of classical theism. For example, what were the other divinities doing all by their lonesome from eternity? From whence comes the Subject-Object relation? God is a relation of three, co-eternal persons in one. In any event, make no mistake about it, God's existence is manifestly rational and necessary.