Two sorts of truth: profound truths — recognized by the fact that the opposite is also a profound truth, — in contrast to trivialities where opposites are obviously absurd.

Niels Bohr (1885-1962) Danish physicist

(Attributed)

As quoted in Hans Bohr, "My Father", in Niels Bohr: His Life and Work (1967).

Variants:

• " The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth."
• "It is the hallmark of any deep truth that its negation is also a deep truth." [Quoted in Max Delbrück, Mind from Matter: An Essay on Evolutionary Epistemology, (1986)]