Aphorism

An aphorism is a memorable saying. It often contains a surprising truth. Most aphorisms are quite short, but not all:

Ars longa, vita brevis (Art is long but life is short). Hippocrates' opening to his work on medicine.
To do nothing is sometimes a good remedy. Hippocrates.
The various modes of worship, which prevailed in the Roman world, were all considered by the people, as equally true; by the philosopher, as equally false; and by the magistrate, as equally useful. Edward Gibbon, "The Decline and Fall of the Roman Empire", volume 1, chapter 1.
Power tends to corrupt, and absolute power corrupts absolutely. Lord Acton (John Dalby-Acton, 1st Baron Acton), in The history of freedom in antiquity (1877).
Our virtues are most frequently but vices in disguise. ("Nos vertus ne sont, le plus souvent, que de vices déguisés".) Francois de La Rochefoucauld. Reflections; or Sentences and Moral Maxims (1665–1678)
We are all in the gutter, but some of us are looking at the stars. Oscar Wilde, in Lady Windermere's Fan (1892).
Fool, nothing is impossible in Russia but reform. Oscar Wilde, in Vera; or, The Nihilists (1880).
All is flux, and You cannot step into the same river twice. Both quoted by Plato in his Cratylus, and both were remarks of Heraclitus. But Plato's version was not quite the same. The first was All entities move and nothing remains still.