Antithesis

Antithesis places two contrasting ideas in parallel grammatical form within the same sentence, so that the balance of the construction sharpens the opposition between them.

The contract was generous to the publisher and insulting to the writer.

Two halves, identically built, pointing opposite ways. Antithesis is parallelism put to work on a contrast: the matched grammar is what makes the opposition feel exact rather than merely stated.

Compare the unbalanced version — The contract was generous to the publisher, though the writer was not treated very well — which contains the same contrast and none of the force. The symmetry is the argument.

Dickens opens A Tale of Two Cities with a sustained run of it — It was the best of times, it was the worst of times — and the whole paragraph works by refusing to choose between its halves.

Two practical uses. It is the natural form for a character stating a position, because it sounds decided, which is also why a character who speaks in antithesis reads as either formidable or insufferable. And it is a strong closing sentence for an argument, since the balance gives an impression of having weighed both sides.

Keep it distinct from its neighbours. Oxymoron puts contradictory terms side by side in one phrase. Paradox makes a statement that contradicts itself and turns out to be true. Antithesis simply opposes two things, in balance, and means both halves plainly.