act of faith

An act of faith is something done based on trust or belief rather than proof or certainty.

The phrase often describes decisions made without guarantee of success, where one proceeds on conviction alone: Hiring someone with no experience was an act of faith.

In religious contexts, it refers to demonstrations of spiritual belief, but secular usage has broadened to cover any leap of trust—investing in an unproven idea, giving someone a second chance, or committing to something despite uncertainty.