Adam Gopnik in The New Yorker:
Almost all books of aphorisms, which have ever acquired a reputation, have retained it,” John Stuart Mill wrote in 1837, aphoristically—that is to say, with a neat if slightly dubious finality. (“How wofully the reverse is the case with systems of philosophy,” he added.) We prefer collections of aphorisms over big books of philosophy, Mill thought, not just because the contents are always short and usually funny but because the aphorism is, in its algebraic abbreviation, a micro-model of empirical inquiry. Mill noted that “to be unsystematic is of the essence of all truths which rest on specific experiment,” and that there is, in a good aphorism, “generally truth, or a bold approach to some truth.” So when La Rochefoucauld writes, “In the misfortune of even our best friends, there is something that does not displease us,” he is offering not a moral injunction saying “Take pleasure in the misfortune of your best friends” but a testable observation about what Mill termed “the workings of habitual selfishness in the human breast.” The aphorism means: We do take pleasure—not in every case, perhaps, but more often than we might admit—in the misfortune of our best friends.
We don’t absorb aphorisms as esoteric wisdom; we test them against our own experience. The empirical test of the aphorism takes the form first of laughter and then of longevity, and its confidential tone makes it candid, not cynical. Aphorisms live because they contain human truth, as Mill saw, and reach across barriers of class and era. “Old men delight in giving good advice as a consolation for the fact that they can no longer set bad examples,” another La Rochefoucauld classic, is not only humorous in its tidy reversal; it is also still rather persuasive, as we watch the drift from rebelliousness to reaction in every generation.
Aphorisms come at us in so many forms and from so many periods that one might think an academic study of aphorisms would aim to give them a family tree—tracing the emergence of the humanistic aphorism from its solemn white-bearded grandfather, the proverb; the descent of the clever, provocative epigram from its sly guerrilla progenitor, the parable (the form that allowed Jesus to spread subversion while seeming merely obscurely elegant). And then we might learn how those later forms have spawned such contemporary commercial descendants as the one-liner and the meme.
More here.