In regard to the philosophers, if they be true philosophers, i.e., lovers of truth, they should not be irritated that the earth moves. Rather, if they realize that they have held a false belief, they should thank those have shown them the truth; and if their opinion stands firm that the earth doesn't move, they will have reason to boast than be angered.

I would beg the wise and learned fathers [of the church] to consider with all diligence the difference which exists between matters of mere opinion and matters of demonstration.

It was granted to me alone to discover all the new phenomena in the sky and nothing to anybody else. This is the truth which neither envy nor malice can supress.

The Universe is a grand book which cannot be read until one first learns to comprehend the language and become familiar with the characters in which it is composed. It is written in the language of mathematics.

Nothing can be taught to a man, only it's possibly to help him to discover it inside.

I do not think it is necessary to believe that the same God who has given us our senses, reason, and intelligence wished us to abandon their use, giving us by some other means the information that we could gain through them.

But, because my private lectures and domestic pupils are a great hinderance and intteruption of my studies, I wish to live entirely exempt from the former, and in great measure from the latter. ... in short, I should wish to gain my bread from my writings.