Should I not be proud, when for twenty years I have had to admit to myself that the great Newton and all the mathematicians and noble calculators along with him were involved in a decisive error with respect to the doctrine of color, and that I among millions was the only one who knew what was right in this great subject of nature?

Everything factual is, in a sense, theory. The blue of the sky exhibits the basic laws of chromatics. There is no sense in looking for something behind phenomena: they are theory.

Of all thieves, fools are the worst; they rob you of time and temper.

Most pioneers are at the mercy of doubt at the beginning, whether of their worth, of their theories, or of the whole enigmatic field in which they labour.

Nothing is so atrocious as fancy without taste.

There are men who never err, because they never propose anything rational.

One never goes further than when they do not know where they are going.