Battle not with monsters, lest ye become a monster, and if you gaze into the abyss, the abyss gazes also into you. - Friedrich Nietzsche

When you look into an abyss, the abyss also looks into you.

Mathematics would certainly have not come into existence if one had known from the beginning that there was in nature no exactly straight line, no actual circle, no absolute magnitude.

They devour each other and cannot even digest themselves.

It is the business of the very few to be independent; it is a privilege of the strong. And whoever attempts it, even with the best right, but without being OBLIGED to do so, proves that he is probably not only strong, but also daring beyond measure. He enters into a labyrinth, he multiplies a thousandfold the dangers which life in itself already brings with it; not the least of which is that no one can see how and where he loses his way, becomes isolated, and is torn piecemeal by some minotaur of conscience. Supposing such a one comes to grief, it is so far from the comprehension of men that they neither feel it, nor sympathize with it. And he cannot any longer go back! He cannot even go back again to the sympathy of men!