ABSTRACT
Assertions by Greek thinkers, especially by the Stoics, that man alone of animals possesses reason were often accompanied, as a sort of corollary, by the claim that reason-possession confers moral superiority. The Stoics argued that rationality confers upon a being a value and standing that non-rational beings lack.2 Rationality “matters,” because absence of reason excludes an irrational being from moral considerability. If man alone of animals possesses reason, the Stoics argued, a human being has no obligations to other animal species: man “owes” them nothing. This stance has reemerged in contemporary philosophical discourse, when philosophers ask whether humans may justly overlook any interests that non-human animals may have in their own existence. In this chapter, we examine the case for the moral significance of rationality as it manifested itself in ancient thought, beginning with an analysis of how Stoic ethical philosophy, under influence from Aristotle, was, already in its most basic assumptions, predisposed to exclude non-human species from the sphere of human moral considerability, and we discuss the survival of this position in modern philosophical and scientific debate in an effort to understand why reason-possession was viewed as conferring value to rational beings and granting priority to their interests over those of non-rational beings that were consequently judged to lack moral standing. We shall also examine ancient and modern counterclaims that human beings, even if possessed of intellectual faculties superior to those identifiable in other animals, do not in fact differ from non-human animals in morally significant ways, and are not unique in possessing moral standing. The majority of the arguments encountered in modern philosophical and ethological debate on the moral dimensions of reason-possession for non-human animals find parallels in classical sources.
