Faith is a knowledge within the heart, beyond the reach of proof.
Getting ahead in a difficult profession requires avid faith in yourself. That is why some people with mediocre talent, but with great inner drive, go so much further than people with vastly superior talent.
Christianity emerged from the religion of Israel. Or rather, it has as its background a persistent strain in that religion. To that strain Christians have looked back, and rightly, as the preparation in history for their faith.