- All truths are easy to understand once they are discovered; the point is to discover them.
- Eppur si muove
- "And yet it [the earth] moves" or "but it moves" is a comment he is rumored to have made after his recantation before the Inquisition.
- I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forego their use.
- Ic nǽfre métte mann swá dwǽs þe ic of him ne cúðe lǽran áwiht.
- If you could see the earth illuminated when you were in a place as dark as night, it would look to you more splendid than the moon.
- In questions of science the authority of a thousand is not worth the humble reasoning of a single individual.
- 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?
- Philosophy is written in this grand book— I mean the universe— which stands continually open to our gaze, but it cannot be understood unless one first learns to comprehend the language in which it is written. It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures, without which it is humanly impossible to understand a single word of it; without these, one is wandering about in a dark labyrinth (1623)
- The Bible tells us how to go to the heavens, not how the heavens go.
- What has philosophy got to do with measuring áhwæt?
- Wín is "léoht héold ætgæddre þurh wǽtnesse."
- Þu ne canst lǽran sumne mann áhwæt, þu canst ánlíce him helpan tó findenne hit for him selfum.