Leap of faith
A term coined by Kierkegaard to describe the act of committing to religious belief — or to any sustaining meaning — in the absence of rational proof. For Kierkegaard, no chain of argument can deliver you across the gap between worldly despair and authentic spiritual life; the gap can only be crossed by a deliberate, non-rational leap. The phrase has since been generalised to any commitment that requires acting beyond what reason alone can justify, and remains the central image in existentialist accounts of how a finite human can relate to the infinite.