This quote is patently untrue. For example, is it true that circles are round? Yes. Was that truth ever ridiculed? No. Was it violently opposed? No. Same with "triangles have three sides": never ridiculed, never opposed. Many other examples: the Sun is hot, the sky is blue, we all have a biological mother and father... Ok, so that's ridicule and opposition. What the "self-evident" part? Pythogoras' Theorem. It's true that the square of the hypotenuse is equal to the sum of the squares of the two adjacent sides for right angled triangles. Is that "self-evident"? Not really; it took someone to derive it. That all Earthly matter is composed of atoms is true, but not self-evident.There's an infinity of other examples... the Schopenhauer quote is often used, very seldom actually thought about. It's basically false, however attractive and profound it might seem for the first two seconds.