Only humans are capable of reason

The argument

This argument grounds humanity's licence to use the environment for its own ends in a claim about what sets humans apart: the capacity for reason. On this view, human beings are uniquely rational — able to think abstractly, deliberate, form moral judgements, plan for the future, and understand the world conceptually — in a way that no other animal or natural entity can. This rational capacity has long been held, in a tradition running from Aristotle through the Stoics and into much of Western philosophy, to mark humans out as a fundamentally different kind of being, possessing a dignity and standing that the rest of nature lacks. The moral conclusion drawn is that the natural world exists, in effect, as a resource for rational beings to use. If only humans can reason, then only humans are full members of the moral community — only they can hold rights, bear duties and pursue chosen ends — while plants, animals and ecosystems, lacking reason, have value primarily in relation to human purposes rather than in themselves. Their worth is instrumental: they are means to human flourishing, raw material that rational agents may shape and consume to meet their needs and advance their projects. On this account, there is nothing wrong in principle with exploiting the environment for human benefit, because the environment is precisely the kind of thing that exists to be used. From this standpoint, human superiority is not arrogance but a recognition of a real and morally significant difference in kind. Rational beings stand above non-rational nature and are entitled to draw on it for their advantage. Because only humans are capable of reason, and reason confers a higher moral standing, this argument holds, humans may legitimately use the environment for its instrumental value rather than being bound to care for it as an end.

Premises

Counter-arguments

Critics answer that reason is a poor criterion for moral standing, because it would exclude infants, the severely cognitively impaired and the comatose from the moral community — which almost no one accepts — so the capacity that supposedly licenses using nature does not track who deserves moral consideration. They argue that sentience, the capacity to suffer, is a more defensible ground, on which many animals have interests that constrain how we may treat them. Even granting human distinctiveness, they add, superiority in reasoning does not entail entitlement to exploit; prudential and intergenerational reasons to protect ecosystems remain, so instrumental value is not a licence for unrestrained use.

Rejecting the premises

[Rejecting P2] Making rationality the criterion of moral standing would exclude infants and the severely cognitively impaired, which almost no one accepts, so reason does not reliably mark who merits moral consideration. [Rejecting P3] Even if humans are uniquely rational, superiority in reasoning does not entail a licence to exploit; sentient animals have interests, and prudential and intergenerational reasons still constrain how nature may be used.