Everyone has some faith in an ultimate something that cannot be substantiated solely by physical evidence.
Atheists have faith in naturalism alone - their faith is nakedly exposed in topics such as the origin of life or, as they term it, abiogeneis. Abiogenesis is the idea that life originated from non-living matter in the sense that it arose naturalistically. The naturalistic (and therefore “scientific”) concept is that life ("bio") must have originated ("genesis") without ("a-") any outside help.
Life, ALL BIOLOGICAL LIFE anywhere in the universe, ultimately either arose naturally or supernaturally. So, ultimately, there are really only two alternatives.
With abiogenesis, atheists must ulimately rely upon the "unknown process" of the gaps in contrast to the theists' so called "God of the gaps" argument (a criticism of ID). The reason this explanation is not any better than their own sarcastic carature of God, the Flying Spagettii Monster (FSM), is that we know what the raw chemicals are capable of doing (or NOT doing, in this case) and we know that the overall reactions produce results that go in the wrong direction (away from life). All the origin of life experiments are failures at providing anything that actually works... but since the atheists "knows" that the materialistic universe is all that exists, he invokes his own mantra about unknown conditions and processes and convinces others that THIS is the only logical and scientific response in spite of the resulting facts.
To put it bluntly, naturalistic scientists do not really have a clue how life arose. They have a bunch of "just so" stories and THAT is ALL! Their experiments are absolute dead ends. But, hopefully, "someday" (they believe) scientists may eventually find those "unknown processes" which will allow matter to self-organize into the bio-chemical equivalent of a von Neumann machine (named for mathematician and founder of cybernetics, John von Neumann (1903-1957).
The “simple” cell remains a staggering example of the stupendous complexity required for even the simplest bio-chemical “von Neumann” self-repairing, self-reproducing, metabolizing machine to exist. And in an environment where malfunctions equal death, is it really probable that such “mechanisms” could evolve by natural processes? Not likely. In fact, it is highly unlikely that many of the sub-cellular molecular machines found within a single cell could evolve by natural processes.
Theists believe that the God that exists has revealed himself. Is there faith involved? Absolutely! The question isn’t whether or not faith is involved (we ALL have faith in things we can’t demonstrate to be true empirically) but whether or not that faith is reasonable. The problem then becomes defining what is reasonable. Evidence, it seems, is not regarded as evidence until it is first PERCIEVED to actually be evidence. It was not too long ago when evidence that stones were falling from the sky was denounced as impossible because everyone just “knew” that stones could not fall from the sky. Today we call these stones meteorites. The evidence was there but the belief paradigm at that time would not accept it. In other words, we all filter out what the evidence really is based on our world-view or basic belief paradigm. We are all prejudiced. So, which bias is the best bias to be biased with? I believe the theistic bias is a very good bias...