Natural right, in Nietzsche, in Strauss.

[Sauwelios]

In the Introduction to one of the first books he wrote in English, Leo Strauss said:

Natural right in its classic form is connected with a teleological view of the universe. All natural beings have a natural end, a natural destiny, which determines what kind of operation is good for them. In the case of man, reason is required for discerning these operations: reason determines what is by nature right with ultimate regard to man's natural end. The teleological view of the universe, of which the teleological view of man forms a part, would seem to have been destroyed by modern natural science. From the point of view of Aristotle---and who could dare to claim to be a better judge in this matter than Aristotle?---the issue between the mechanical and the teleological conception of the universe is decided by the manner in which the problem of the heavens, the heavenly bodies, and their motion is solved. Now in this respect, which from Aristotle's own point of view was the decisive one, the issue seems to have been decided in favor of the nonteleological conception of the universe. Two opposite conclusions could be drawn from this momentous decision. According to one, the nonteleological conception of the universe must be followed up by a nonteleological conception of human life. But this "naturalistic" solution is exposed to grave difficulties: it seems to be impossible to give an adequate account of human ends by conceiving of them merely as posited by desires or impulses. Therefore, the alternative solution has prevailed. This means that people were forced to accept a fundamental, typically modern, dualism of a nonteleological natural science and a teleological science of man. [...] The fundamental dilemma, in whose grip we are, is caused by the victory of modern natural science. An adequate solution to the problem of natural right cannot be found before this basic problem has been solved.
Needless to say, the present lectures [i.e., the actual chapters of the book] cannot deal with this problem. [Strauss, Natural Right and History (1953), pp. 7-8.]

I think that Strauss actually found the solution to this problem near the end of his life. In the central essay, mind you, of the essays comprising his last book, he said:

To recognize the crucial importance of cruelty is indispensable if "the terrible basic text homo natura," "that eternal basic text" is again to be seen, if man is to be "re-translated into nature." That re-translation is altogether a task for the future: "there never was yet a natural humanity" (Will to Power nr. 120). Man must be "made natural" (vernatürlicht) together "with the pure, newly found, newly redeemed nature" (The Gay Science aph. 109). For a man is the not yet fixed, not yet established beast (aph. 62): man becomes natural by acquiring his final, fixed character. For the nature of a being is its end, its completed state, its peak (Aristotle, Politics 1252b 32-34). "I too speak of 'return to nature,' although it is properly not a going back but an ascent---up into the high, free, even terrible nature and naturalness..." (Twilight of the Idols, 'Skirmishes of an untimely man' nr. 48). Man reaches his peak through and in the philosopher of the future as the truly complementary man in whom not only man but the rest of existence is justified (aph. 207). [Strauss, Studies in Platonic Political Philosophy (1973), page 189.]

The philosopher of the future is the natural end of man in the sense that he is at the same time 1) man's peak and 2) natural in the sense of "the pure, newly found, newly redeemed nature", which is in effect nature according to modern natural science (cf. Beyond Good and Evil aph. 22). He is man's completed state:

I teach: that there are higher and lower men, and that a single individual can under certain circumstances justify the existence of whole millennia---that is, a full, rich, great, whole human being in relation to countless incomplete fragmentary men. [Will to Power nr. 997 (1884), entire, trans. Kaufmann.]

And he is natural---highly, freely, even terribly natural:

NB. The highest man [is] to be conceived of as an image of nature: monstrous abundance, monstrous reason in the particular, as a whole squandering himself, indifferent thereto:------ [Nietzsche, Nachlass Spring 1884 25 [140], entire, my translation.]

From this it follows, in the language of the Introduction to Natural Right and History, that that kind of operation is good for man which brings him closer to being a philosopher of the future. Note by the way that this natural end is not natural in that "the Vernatürlichung of man [...] is by no means necessary but requires a free, creative act" (Strauss, SPPP ibid.); it is natural only in that the philosopher of the future is the vernatürlicht man---the man who is truly "an image of nature".