上句见：Day259
The Story of Philosophy《哲学的故事》第1章Plato第4节IV. The Ethical Problem第4段引文第4句：

This, of course, is the doctrine which our own day more or less correctly associates with the name of Nietzsche. "Verily I laughed many a time over the weaklings who thought themselves good because they had lame paws."11 Stirner expressed the idea briefly when he said that "a handful of might is better than a bagful of right." Perhaps nowhere in the history of philosophy is the doctrine better formulated than by Plato himself in another dialogue, Gorgias (483 f), where the Sophist Calicoes denounces morality as an invention of the weak to neutralize the strength of the strong.
They distribute praise and censure with a view to their own interests; they say that dishonesty is shameful and unjust — meaning by dishonesty the desire to have more than their neighbors; for knowing their own inferiority, they would be only too glad to have equality…. But if there were a man who had sufficient force [enter the Superman], he would shake off and break through and escape from all this; he would trample under foot all our formulas and spells and charms, and our laws, that sin against nature…. He who would truly live ought to allow his desires to wax to the uttermost; but when they have grown to their greatest he should have courage and intelligence to minister to them, and to satisfy all his longings. And this I affirm to be natural justice and nobility. But the many cannot do this; and therefore they blame such persons, because they are ashamed of their own inability, which they desire to conceal; and hence they call intemperance base…. They enslave the nobler natures, and they praise justice only because they are cowards.
11Thus Spake Zarathustra, New York, 1906, P.166
浙江大学译本：我断言这才是自然的正义和高贵。

解析

1、And this I affirm to be natural justice and nobility.
我断言这才是自然的正义和高尚。

这句是观点句。前句中让欲望任意滋长、用勇气与智慧满足所有渴望的生活才是真正的生活，才是自然的正义和高尚。柏拉图提倡自然主义的道德。