In Natural Right and History, Strauss's silence about Aristotle's biology weakens the argument for natural right at crucial points where an appeal to Aristotelian biology would strengthen the argument.
For example, as I have indicated in many posts, Strauss's claim at the beginning of his book that the teleology of natural right depends on the science of the heavens ignores Aristotle's argument for a purely biological teleology.
A second example is the passage where Strauss appeals to "an empirical science of man" based on man's natural sociality. Strauss writes:
The phenomenon of admiration of human excellence cannot be explained on hedonistic or utilitarian grounds, except by means of ad hoc hypotheses. These hypotheses lead to the assertion that all admiration is, at best, a kind of telescoped calculation of benefits for ourselves. They are the outcome of a materialistic or crypto-materialistic view, which forces its holders to understand the higher as nothing but the effect of the lower, or which prevents them from considering the possibility that there are phenomena which are simply irreducible to their conditions, that there are phenomena that form a class by themselves. The hypotheses in question are not conceived in the spirit of an empirical science of man.Strauss is drawing here from Aristotle's famous passage in Politics (1253a7-38) about man as being by nature the most political animal. But Strauss does not indicate that for Aristotle this "empirical science of man" is part of the biological science of political animals, which Aristotle lays out in his biological writings (HA, 488a8-14, 553a26-54b26, 588b23-89a9, 614b19-26, 623b26-29a30). If Strauss had done that, he might have raised the question as to whether modern Darwinian biology supports this. And he might have noticed that in the Descent of Man, Darwin agrees with everything that is said in the above passage--the inadequacy of hedonistic utilitarianism in explaining the human admiration for excellence, the natural sociality of human beings, the importance of language in distinguishing human beings, the moral sentiments ("love, affection, friendship, pity"), and the naturalness of moral judgement as rooted in human nature. Moreover, Strauss might have noticed that the modern idea of emergent evolution recognizes that the higher phenomena of the living world are irreducible to the lower phenomena of the physical world.
Man is by nature a social being. He is so constituted that he cannot live, or live well, except by living with others. Since it is reason or speech that distinguishes him from the other animals, and speech is communication, man is social in a more radical sense than any other social animal: humanity itself is sociality. Man refers himself to others, or rather he is referred to others, in every human act, regardless of whether that act is 'social' or 'antisocial.' His sociality does not proceed, then, from a calculation of the pleasures which he expects from association, but he derives pleasure from association because he is by nature social. Love, affection, friendship, pity, are as natural to him as concern with his own good. It is man's natural sociality that is the basis of natural right in the narrow or strict sense of right. Because man is by nature social, the perfection of his nature includes the social virtue par excellence, justice; justice and right are natural. All members of the same species are akin to one another. This natural kinship is deepened and transfigured in the case of man as a consequence of his radical sociality. In the case of man the individual's concern with procreation is only a part of his concern with the preservation of the species. (128-29)
Both Aristotle and Darwin saw that the natural sociality of human beings was an extension of the first social bond between parents and offspring. The affiliative bonding of parents and children is extended over ever-larger groups. As compared with other animals, the extended period of offspring dependence on parental care and the complexity of the social learning during this period manifests the connection between human sociality and human rationality, in that human reason is adapted for navigating through the intricacies of human social life. The Darwinian understanding of this link between rationality and sociality has been deepened by contemporary Darwinian scientists exploring the "social brain" hypothesis. The fundamental conclusion of this Aristotelian and Darwinian understanding is that human beings are by nature the most rational animals because they are by nature the most political animals.
If "man's natural sociality" is "the basis of natural right in the narrow or strict sense of right," then Aristotelian and Darwinian biology supports natural right by explaining the biological nature of this natural sociality and the natural rationality to which it is tied.
A third example in Natural Right and History of where Strauss is unreasonably silent about Aristotle's biology is in the account of Locke. Strauss assumes that Locke's political philosophy rejected the rule of nature in favor of the rule of convention. This reading of Locke is mistaken, because it fails to recognize that in criticizing the Platonic naturalism of eternal essences, Locke is defending a biologically empirical science of natural history that points back to Aristotle and ahead to Darwin.
I have elaborated this last point in a previous post.
My general conclusion is that Aristotle helps us to see that the study of the human things and of the human quest for natural right is a biological study of human beings compared with other animals.
"In the works of nature, purpose and not accident is predominant; and the purpose or end for the sake of which those works have been constructed or formed has its place among what is beautiful. If, however, there is anyone who holds that the study of animals is an unworthy pursuit, he ought to go further and hold the same opinion about the study of himself" (PA, 645a25-28).