Nature...does not act by means of many things when it can do so by means of a few.

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

See now the power of truth.

Alas! Your dear friend and servant Galileo has been for the last month hopelessly blind; so that this heaven, this earth, this universe, which I by my marvelous discoveries and clear demonstrations had enlarged a hundred thousand times beyond the belief of the wise men of bygone ages, henceforward for me is shrunk into such a small space as is filled by my own bodily sensations.

To be humane, we must ever be ready to pronounce that wise, ingenious and modest statement 'I do not know'.

Vision, I say, is related to light itself. But of this sensation and the things pertaining to it, I pretend to understand but little; and since even a long time would not suffice to explain that trifle, or even to hint at an explanation, I pass over this in silence.

I do not know what to say in a case so surprising, so unlooked for and so novel.