The animal tends to eat with its stomach, and the man with his brain. When the animal’s stomach is full, he stops eating, but the man is never sure when to stop. When he has eaten as much as his belly can take, he still feels empty, he still feels an urge for further gratification. This is largely due to anxiety, to the knowledge that a constant supply of food is uncertain. Therefore eat as much as you can while you can. It is due, also, to the knowledge that, in an insecure world pleasure is uncertain. Therefore the immediate pleasure of eating must be exploited to the full, even though it does violence to the digestion.

Human desire tends to be insatiable. We are so anxious for pleasure that we can never get enough of it. We stimulate our sense organs until they become insensitive, so that if pleasure is to continue they must have stronger and stronger stimulants. In self-defence the body gets ill from the strain, but the body wants to go on and on. The brain is in pursuit of happiness, and because the brain is much more concerned about the future than the present it conceives happiness as the guarantee of an indefinitely long future of pleasures. Yet the brain also knows that it does not have an indefinitely long future, so that, to be happy, it must try to crowd all of the pleasures of paradise and eternity into the span of a few years.

This is why modern civilization is in almost every respect a vicious circle.