Different people have different definitions of the word "faith". Some people favour the definition "belief without evidence." Some particularly silly atheists even claim it is belief in spite of the evidence. But God takes a very different approach. In Hebrews 11:1, we read "Now faith is the substance of things hoped for, the evidence of things not seen." (NKJV).
Even proponents of the definition that faith is belief in spite of evidence have faith. In fact, different people require different levels of faith for everything. A blind man, for example, cannot see the sun. If he has been blind since birth, he wouldn't have any proof that the sun exists. He can't see it because he's blind. He can't hear it because the sound it makes can't travel this far. He can't smell it for the same reason. He cannot taste or touch it because even if he could get close enough to do so, he would be long dead before he got within range. Long story short, the only reason people who have been blind since birth know the sun exists is because we, who can see, have told them.
There are ways to provide evidence for the sun. Witness testimony is one of them. I see the sun, I tell a blind person the sun exists, that's evidence that the blind man can reasonably rely on. I could take them outside and let them feel the heat. Some blind people are capable of telling the difference between light and dark, so I could direct them to the sun and they could at least know they are facing a light-producing object.
But all of these things could be discounted. A blind man can assume that when we talk about the sun, we're lying. Big prank, perhaps? Or maybe we're even blind, too, we're just better at living with it than they are. Heat can be generated in a number of ways. Some water parks have tall radiator things designed to heat you up so you dry off after a wet ride. How could the blind man tell the difference between the sun and one of those? The point is, a blind man could deny the existence of the sun, and one could argue it's even reasonable for him to do so, even if he's completely wrong.
So, faith can be required to accept truth. Just as a blind man cannot see the sun, so also can we not directly see a lot of things, theologically speaking. We cannot see the origins of the universe. We cannot see the origins of our species. We cannot see the miracles described in the Bible. We can't even see the "regular" (i.e. non-supernatural) historical events described in the Bible. We can't see Heaven, and we can't see Hell (yet). No one living has ever seen any of these things, because they cannot be seen. Some people might disagree. Atheists often claim they can scientifically prove Evolution, or prove that there is no God, or that death is absolutely the end and there is no supernatural. But they can't. They can neither be proven or disproven. In reality, it takes as much faith (arguably more) to reject the Bible as it does to accept it.
Just as there is evidence for the sun that can be given to a blind man, there is evidence for the Son that can be provided to an unbeliever. You cannot fully prove the Bible. You can prove elements of it, but to prove it entirely is impossible. But just as a blind man would be wrong to reject the existence of the sun, so also is an unbeliever wrong to reject the truth of the Bible. Sufficient evidence exists in numerous academic fields. It takes faith, but that leap of faith is worth taking.