What is faith?

One of the most persistent and compelling ideas I’ve learned recently is what Jim Collins calls the Stockdale paradox.
It's named for the American admiral who survived eight years in the notorious Vietnamese Hanoi Hilton prison camp and sustained his men’s spirits (and his own) with this mindset:
Maintain absolute conviction that you will prevail while confronting the brutal facts on the ground.
To understand faith requires understanding the difference between hope and optimism.
Optimism relies on the expectation that fate is on our side.
Hope emerges from the confidence that fate does not determine our future.
We have faith in those who earn our trust. If we study the wisdom of the ages, we acquire faith in the Almighty.
If we live based on the values of discipline, determination, and courage, we have faith in ourselves, and faith that we are worthy of divine intervention.
Most of all, if we recognize, as J.B.S. Haldane observed,
that the Universe is not only queerer than we suppose, but queerer than we can suppose,
then we will be filled with a sense of wonder and humility that awaken in us the ultimate faith,
the faith that there is a plan at work beyond our comprehension,
the faith that we have a critical part to play,
and the faith that, no matter how brutal the facts on the ground, we will prevail.