Humanity will find in itself the power to live for virtue even without believing in immortality.
 Fyodor Dostoyevsky, The Brothers Karamazov (1880). copy citation

Context

“Not for scoundrels, but for pedantic poseurs, ‘haunted by profound, unsolved doubts.’ He's showing off, and what it all comes to is, ‘on the one hand we cannot but admit’ and ‘on the other it must be confessed!’ His whole theory is a fraud! Humanity will find in itself the power to live for virtue even without believing in immortality. It will find it in love for freedom, for equality, for fraternity.” Rakitin could hardly restrain himself in his heat, but, suddenly, as though remembering something, he stopped short. “Well, that's enough,”” source