Aristotle's metaphysics, roughly speaking, may be described as Plato diluted by common sense. He is difficult because Plato and common sense do not mix easily.

The luxury to disparage freedom is the privilege of those who already possess it.

When Benjamin Franklin invented the lightning-rod, the clergy, both in England and America, with enthusiastic support of George III, condemned it as an impious attempt to defeat the will of God.

A world full of happiness is not beyond human power to create; the obstacles imposed by inanimate nature are not insuperable. The real obstacles lie in the heart of man, and the cure for these is a firm hope, informed and fortified by thought.

There are certain things that our age needs, and certain things that it should avoid. It needs compassion and a wish that mankind should be happy; it needs the desire for knowledge and the determination to eschew pleasant myths; it needs, above all, courageous hope and the impulse to creativeness.

If a Black Death could be spread throughout the world once in every generation survivors could procreate freely without making the world too full.

Next to worry probably one of the most potent causes of unhappiness is envy.