Galileo Galilei

The greater the number of facts, the greater the certainty.

Ignorance is the root of all evil.

The motion of the Earth is a fact, and not a theory.

I have discovered in the heavens many things that had not been seen before my time.

The Earth is a globe, and it moves.

The true philosophy is that which is written in the great book of the universe.

It is not enough to have a good mind; the main thing is to use it well.

I found the most beautiful things in the heavens.

The purpose of science is to discover the truth, not to defend a dogma.

Truth is the daughter of time, not of authority.

The universe is governed by immutable laws, which can be discovered by human reason.

Nature is written in that great book which ever lies before our eyes — I mean the universe — but we cannot understand it unless we first learn the language and apprehend the symbols in which it is composed.

I think that in the discussion of natural problems we ought to begin not with the Scriptures, but with experiments and demonstrations.

E pur si muove! (And yet it moves!)

The greater the obstacle, the more glory in overcoming it.

It is a beautiful and admirable thing to know that the human mind is capable of such ingenuity as to discover the motions of the planets.

Philosophy is written in this grand book, the universe, which stands continually open to our gaze. But the book cannot be understood unless one first learns to comprehend the language and interpret the characters in which it is written. It is written in the language of mathematics, and its characters are triangles, circles, and other geometrical figures, without which it is humanly impossible to understand a single word of it; without these, one is wandering about in a dark labyrinth.

To forbid us anything is to make us have a mind for it.

The senses, however, though they may be deceived, are not always so.

It is not in the power of any created being to make a truth false.