Measure what is measurable, and make measurable what is not so.

Nothing occurs contrary to nature except the impossible, and that never occurs.

Showing a greater fondness for their own opinions than for truth, they sought to deny and disprove the new things which, if they had cared to look for themselves, their own senses would have demonstrated to them.

My dear Kepler, what would you say of the learned here, who, replete with the pertinacity of the asp, have steadfastly refused to cast a glance through the telescope? What shall we make of this? Shall we laugh, or shall we cry?

You cannot teach a person something he does not already know, you can only bring what he does know to his awareness.

You may force me to say what you wish; you may revile me for saying what I do. But it moves.

The doctrine that the earth is neither the center of the universe nor immovable, but moves even with a daily rotation, is absurd, and both philosophically and theologically false, and at the least an error of faith.