Fervent religious believers sacrifice pleasures of the body, but instead enjoy pleasures of the mind, including the joy of knowing that those men who didn't follow their religion would be tortured for eternity.

In spreading his ideas, Plato was willing to employ emotional appeals, state propaganda, and the use of force.

The psychology of adultery has been falsified by conventional morals, which assume, in monogamous countries, that attraction to one person cannot coexist with affection for another. Everybody knows that this is untrue.

They must often change, who would be constant in happiness or wisdom. Those who continually search for happiness will never find it. Happiness is made, not found. To be without some of the things you want is an indispensable part of happiness.

[There are m]oral precepts that we consider really important, such as 'don't pick your nose' or 'don't eat peas with a knife'. There may, for ought I know, be admirable reasons for eating peas with a knife, but . . . early persuasion has made me completely incapable of appreciating them.

It will be said that the joy of mental adventure must be rare, that there are few who can appreciate it, and that ordinary education can take no account of so aristocratic a good. I do not believe this. The joy of mental adventure is far commoner in the young than in grown men and women. ...It is rare in later life because everything is done to kill it during education.

What the world needs is not dogma but an attitude of scientific inquiry.