“ Every one will admit that a nature having in perfection all the qualities which we required in a philosopher, is a rare plant which is seldom seen among men. ”
 Plato, The Republic. copy citation

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“And we have next to consider the corruptions of the philosophic nature, why so many are spoiled and so few escape spoiling—I am speaking of those who were said to be useless but not wicked—and, when we have done with them, we will speak of the imitators of philosophy, what manner of men are they who aspire after a profession which is above them and of which they are unworthy, and then, by their manifold inconsistencies, bring upon philosophy, and upon all philosophers, that universal reprobation of which we speak. What are these corruptions? he said. I will see if I can explain them to you. Every one will admit that a nature having in perfection all the qualities which we required in a philosopher, is a rare plant which is seldom seen among men. Rare indeed. And what numberless and powerful causes tend to destroy these rare natures! What causes? In the first place there are their own virtues, their courage, temperance, and the rest of them, every one of which praiseworthy qualities” source