The time of tasks for me is over. If age has brought me anything, it is lightness.

— Alexander Grothendieck, Esquisse d'un Programme (1984).

Mathematics, more than any other art or science, is a young man's game.

— Godfrey Harold Hardy, A Mathematician's Apology (1941).

In so far as a scientific statement speaks about reality, it must be falsifiable.

— Karl Popper, The Logic of Scientific Discovery (1934).

Man is but a reed, the most feeble thing in nature; but he is a thinking reed.

— Blaise Pascal, Pensées, ed. Ch.M des Granges (1964).