When all the thoughts are concerning one thing and the person loses interest in other things, the melancholy begins.

If you do not know the names of things, the knowledge of them is lost, too.

It is not God, but people themselves who shorten their lives by not keeping physically fit.

In natural science the principles of truth ought to be confirmed by observation.

Nature does not proceed by leaps.

The plant kingdom covers the entire earth, offering our senses great pleasure and the delights of summer.

A professor can never better distinguish himself in his work than by encouraging a clever pupil, for the true discovers are among them, as comets amongst the stars.

Stones grow, plants grow, and live, animals grow live and feel.

Blessed be the Lord for the beauty of summer and spring, for the air, the water, the verdure, and the song of birds.

I demand of you, and of the whole world, that you show me a generic character... by which to distinguish between Man and Ape. I myself most assuredly know of none.

Nature's economy shall be the base for our own, for it is immutable, but ours is secondary. An economist without knowledge of nature is therefore like a physicist without knowledge of mathematics.

In Russia I went to a great yeshiva, and in America I work in a carnival.

The enjoyment of life would be instantly gone if you removed the possibility of doing something.

At first I thought I was fighting to save rubber trees, then I thought I was fighting to save the Amazon rain forest. Now I realize I am fighting for humanity

I'm not a do-gooder. It embarrassed me to be classified as a humanitarian. I simply take part in activities that I believe in.

You are good for nothing unless you are clever.

Ultimately, the impresario must know when to simply get out of the way.

We live under a prince who is an enemy to fraud, a prince whose eyes penetrate into the heart, and whom all the art of impostors can't deceive.

To me, the most obscene word in our language is celibacy.

That is a real attitude - to see everything as being meaningful, even the less important things, to prove something, even the greater problems of life.

A man is a hypocrite only when he affects to take a delight in what he does not feel, not because he takes a perverse delight in opposite things.