Aristotle's Nicomachean Ethics hinges on a foundational concept: the "function" or ergon of a human being. This argument posits that understanding what a thing is for, its characteristic activity, is key to discerning its good. For a cobbler, the good is making good shoes; for a harpist, playing well. Extending this to humans, Aristotle concludes that the human good, eudaimonia (often translated as flourishing or living well), is achieved by fulfilling our unique function. This unique function, he argues, is rational activity. Therefore, living well, for a human, means exercising reason excellently. While intuitively appealing in its attempt to ground ethics in observable characteristics, the function argument faces significant philosophical challenges, primarily concerning its teleological assumptions and the very identification of a singular human function. Nevertheless, its historical influence and its success in providing a framework for virtue ethics remain considerable.
The initial step of the function argument involves identifying the ergon of a thing. Aristotle observes that various objects and beings have distinct roles or activities associated with them. A knife's function is to cut; a physician's, to heal. He notes that when something performs its function well, it possesses a virtue relevant to that function. A sharp knife cuts well; a skilled physician heals effectively. The crucial move is then applying this to human beings. Aristotle dismisses a purely biological function, like growth or nutrition, as common to all living things. He also rejects sensory perception, which is shared with animals. Instead, he lands on the faculty of reason as uniquely human: "there is an active life of the rational element." Thus, the human ergon is identified as the soul's activity in accordance with reason, or at least not without reason. This rational activity, when performed excellently over a complete life, constitutes eudaimonia.
However, the argument's reliance on teleology – the idea that things have inherent purposes or ends – has been a persistent point of contention. Critics, particularly from the Enlightenment onwards, have questioned whether attributing inherent purposes to natural objects is philosophically sound. David Hume, for instance, argued that "reason is, and ought only to be the slave of the passions," implying that reason’s role is instrumental rather than constitutive of a fundamental human good. The move from "what a thing does" to "what a thing is for" involves a significant inferential leap. Furthermore, the identification of a single, unifying human function is problematic. Are there not multiple valuable human activities that contribute to a flourishing life, not all exclusively tied to rational activity? Consider artistic creation, athletic prowess, or nurturing relationships; while reason might play a role, they are not solely reducible to it. Michael Walzer, in his critique, suggests that different conceptions of the good life lead to different lists of human goods, undermining the universality Aristotle seems to seek.
Despite these criticisms, the function argument provides a powerful framework for understanding virtue ethics. By linking virtue to the excellent performance of a distinctive human activity, Aristotle offers a compelling account of moral character. Virtues like courage, justice, and temperance are not arbitrary rules but are dispositions that enable us to act rationally and live well in a complex world. For example, courage, understood as the mean between cowardice and recklessness, is a rational way of facing danger that serves the broader good of individual and societal well-being. The function argument, by grounding these virtues in a notion of human flourishing, offers a more robust and coherent account than ethical systems that rely solely on divine command or abstract moral principles. It connects individual character development to a broader conception of a good human life.
In conclusion, Aristotle's function argument, while facing legitimate philosophical objections regarding its teleological underpinnings and the singularity of the human ergon, remains a cornerstone of his ethical theory. Its strength lies in its attempt to provide an objective basis for ethics, linking moral excellence to the fulfillment of our distinct human capacities. By identifying rational activity as the unique human function, Aristotle lays the groundwork for a virtue-based ethics where eudaimonia is achieved through the excellent exercise of reason. While modern philosophy may debate the inherent purposes of nature, the enduring legacy of the function argument lies in its profound influence on Western ethical thought and its insightful exploration of what it means to live a truly human life.