I have never met a man so ignorant that I couldn't learn something from him.

See now the power of truth; the same experiment which at first glance seemed to show one thing, when more carefully examined, assures us of the contrary.

I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use.

You cannot teach a man anything, you can only help him find it within himself.

By denying scientific principles, one may maintain any paradox.

Where the senses fail us, reason must step in.

The sun, with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do.

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.

Philosophy [nature] is written in that great book which ever is before our eyes -- I mean the universe -- but we cannot understand it if we do not first learn the language and grasp the symbols in which it is written. The book is written in mathematical language, and the symbols are triangles, circles and other geometrical figures, without whose help it is impossible to comprehend a single word of it; without which one wanders in vain through a dark labyrinth.

Measure what can be measured, and make measurable what cannot be measured.

(T)he increase of known truths stimulates the investigation, establishment, and growth of the arts.

Names and attributes must be accommodated to the essence of things, and not the essence to the names, since things come first and names afterwards.

I have been in my bed for five weeks, oppressed with weakness and other infirmities from which my age, seventy four years, permits me not to hope release. Added to this (proh dolor! [O misery!]) the sight of my right eye — that eye whose labors (dare I say it) have had such glorious results — is for ever lost. That of the left, which was and is imperfect, is rendered null by continual weeping.

It is a beautiful and delightful sight to behold the body of the Moon.

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

The sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do.

If the Earth were not subject to any change I would consider the Earth a big but useless body in universe, paralyzed...superfluous and unnatural.Those who so exalt incorruptibility, unchangeability and the like, are, I think, reduced to saying such things both because of inordinate desire they have to live for a long time and because of the terror they have of death...they do not realize that if men were immortal, they would have never come into the world.

Surely it is a great thing to increase the numerous host of fixed stars previously visible to the unaided vision, adding countless more which have never before been seen, exposing these plainly to the eye in numbers ten times exceeding the old and familiar stars.

And, believe me, if I were again beginning my studies, I should follow the advice of Plato and start with mathematics.