All the strength and force of man comes from his faith in things unseen. He who believes is strong he who doubts is weak. Strong convictions precede great actions.

Clarke frames human power as fundamentally moral and spiritual rather than merely physical or intellectual. “Faith in things unseen” points to trust in ideals—God, conscience, justice, truth, or a hoped-for future—that cannot be empirically proved in the moment but can nonetheless organize a life. In this view, belief generates steadiness, courage, and endurance; doubt disperses energy and weakens resolve. The final sentence makes the argument practical: decisive action is typically preceded by settled conviction. The quote thus functions as both a defense of religious faith and a broader psychology of motivation, suggesting that commitment to an unseen good is what enables people to attempt difficult, transformative deeds.