← See the axis · Moral circle

The argument from marginal cases

If reason is the criterion, then infants and the severely cognitively impaired do not meet it either, and yet they count fully.

Objects to Anthropocentrism

Singer, Ryder · Animal Liberation · 1975

1. The argument makes reason, responsible agency, the criterion of full moral status.
2. But many humans do not meet it: infants, people with advanced dementia, the severely cognitively impaired can neither promise nor answer for their acts. We nonetheless grant them full dignity.
3. Either one keeps the criterion and excludes these humans, which no one accepts; or one includes them through what they share with animals, the capacity to suffer and to enjoy, and that criterion then holds for animals too.

Therefore So reason cannot be the real criterion: what brings a being into the moral circle is not reasoning but the capacity to suffer, and that many animals have.