When others blindly follow the truth, please remember that nothing is true. When others are restricted by morality or law, remember that everything is allowed. We live in darkness, we serve the light, and we are assassins.

When others blindly pursue the truth, you should remember that everything is empty. When others are bound by morality or law, you should remember that everything is allowed. We serve the light, but we work in the dark.

This is from the later plot of Assassin's Creed 2, and so is the fraternity training new people.