“It has been said that man is a rational animal. All my life I have been searching for evidence that could support this.”

To write a tragedy, a man must feel the tragedy. To feel tragedy, a man must be aware of the world in which he lives. Not only with his mind, but with his blood and sinews.

The demand for certainty is one that is natural to man but is nevertheless an intellectual vice.

The hardest thing to learn in life is which bridge to cross and which to burn.

Freedom of opinion can only exist when the government thinks itself secure.

Most people would sooner die than think; in fact, they do so.

If there were in the world today any large number of people who desired their own happiness more than they desired the unhappiness of others, we could have paradise in a few years.

I hate being all tidy like a book in a library where nobody reads – prison is horribly like that.

Philosophy, from the earliest times, has made greater claims, and achieved fewer results, than any other branch of learning.

No nation was ever so virtuous as each believes itself, and none was ever so wicked as each believes the other.

I consider the official Catholic attitude on divorce, birth control, and censorship exceedingly dangerous to mankind.

Even if all the experts agree, they may well be mistaken.

Few people can be happy unless they hate some other person, nation, or creed.

Sometimes the hardest thing in life is to know which bridge to cross and which to burn.

It seems to me fundamental dishonesty, and a fundamental treachery to intellectual integrity to hold a belief because you think it’s useful and not because you think it’s true.

The fundamental concept in social science is power, in the same sense in which energy is the fundamental concept in physics.

To be able to fill leisure intelligently is the last product of civilization, and at present, very few people have reached this level.

According to the latest figures, 75 percent of Earth’s land surface has been severely altered by humans. Deforestation and unsustainable agriculture as well as the illegal trade of endangered wildlife increase the risk of human-animal contact.

Man is the only creature that consumes without producing. He does not give milk, he does not lay eggs, he is too weak to pull the plough, he cannot run fast enough to catch rabbits. Yet he is lord of all the animals.

Besides love and sympathy, animals exhibit other qualities connected with the social instincts which in us would be called moral.

In the long history of humankind (and animal kind, too) those who learned to collaborate and improvise most effectively have prevailed.

The world is filled with love-play, from animal lust to sublime compassion.

I’m a hard guy to live with. I’m like a caged animal. I’m up all night walking around the living room. It’s hard for me to come down from what I do.

Animals don’t hate, and we’re supposed to be better than them.

Just because an animal is large, it doesn’t mean he doesn’t want kindness.