Two souls dwell, alas! in my breast.

The iron hand of necessity commands, and her stern decree is supreme law, to which the gods even must submit. In deep silence rules the uncounselled sister of eternal fate. Whatever she lays upon thee, endure; perform whatever she commands.

Sing it not in mournful numbers.

Giving is the business of the rich.

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?

Good children's literature appeals not only to the child in the adult, but to the adult in the child.

When the boy begins to understand that the visible point is preceded by an invisible point, that the shortest distance between two points is conceived as a straight line before it is ever drawn with pencil and paper...the fountain of all thought has been opened to him...the philosopher can reveal him nothing new, as a geometrician he has discovered the basis of all thought.