In our superficial life, every formula, every equation, corresponds to a curve or a solid. We have never seen any curve or solid corresponding to my square root of minus one. The horrifying part of the situation is that there exist such curves or solids. Unseen by us they do exist, they must, inevitably; for in mathematics, as on a screen, strange, sharp shadows appear before us. One must remember that mathematics, like death, never makes mistakes, never plays tricks.
