A quote
People say: “What good does it do to point out the obvious?” A great deal of good; for we sometimes know facts without paying attention to them. Advice is not teaching; it merely engages the attention and rouses us, and concentrates the memory, and keeps it from losing grip. We miss much that is set before our very eyes. Advice is, in fact, a sort of exhortation. The mind often tries not to notice even that which lies before our eyes; we must therefore force upon it the knowledge of things that are perfectly well known. One might repeat here the saying of Calvus about Vatinius: “You all know that bribery has been going on, and everyone knows that you know it.”
Seneca·Letter 94 (§25)·trans. Gummere