Whatever the government decides about post-EU regulations on animal sentience, the Greek biographer and essayist Plutarch (died c. ad 120) was fascinated by the comparisons between man and beast and, almost uniquely, argued for the ethical treatment of animals.

Some earlier thinkers contended there was a ‘kinship’ between men and animals because animals had flesh, passions and (being alive) souls. Therefore man should neither eat nor sacrifice them. But then Aristotle (d. 322 bc), who invented the discipline of biology, stepped in. He agreed that animals had desires which caused them to behave in certain ways that looked human, but denied that this was evidence of the ability to reason. Man’s possession of that faculty, together with language, moral concerns, sense of justice (and so on) placed humanity in a quite different league, right at the top of the biological tree. This led later Stoic thinkers to go a step further and argue that, since animals were driven solely by self-interest, with no notion of such concepts as mutual rights, there could be no moral bond between them and man.

Enter Plutarch. Since animals transparently demonstrated a sense of language, purpose, memory, altruism, feelings, care for offspring (and so on), they clearly shared with humans something, however little, of the same conscious world. The fact that they were not identical with humans did not disqualify animals from that basic kinship. In particular, Plutarch was especially keen to nail the claim that animals were not rational. He did this by arguing that ‘nature’ in animals (he hinted here at ‘instinct’) worked together with ‘reason’, e.g. in their ability to use tools. He quoted the case of the hunting dog that, finding no evidence of scent along two branches of a crossroads, instantly chose the third.

Producing myriad examples in three dialogues dealing exclusively with this issue, Plutarch concluded that animals deserved just treatment on the same terms as humans. He was the Attenborough of the ancients.