This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Porphyry's treatise On Abstinence from Killing Animals, written toward the end of the third century, mounts one of the most sustained philosophical arguments for vegetarianism to survive from antiquity, and it does so on two separate grounds that do not entirely sit comfortably together. The first is an argument from justice. Porphyry holds that animals possess a share of rationality, however diminished compared to that of humans, and that this rational nature grounds a claim on our conduct. His governing principle is blunt, it is plainly unjust to harm those who intend no harm against us, and this applies to the animals. Where earlier Greek ethics had generally confined justice to relations among citizens, or at most among rational beings understood to mean human beings, Porphyry extends the circle of moral consideration outward to any creature capable of perception, desire and a rudimentary reasoning about its own good. Killing and eating such a creature, on this argument, is not merely regrettable but a violation of the same principle that forbids harming an innocent human.
The second argument is addressed to a narrower audience, the philosopher pursuing the ascent of the soul rather than the ordinary citizen weighing obligations to neighbors. Here Porphyry's case rests not on what is owed to the animal but on what abstinence does for the one who practices it. Restraint from meat helps a person free himself from the body and the sensible realm as much as possible, loosening the soul's attachment to bodily appetite so that it can turn more readily toward contemplation of the intelligible. This is a familiar Platonist move, treating dietary discipline as one technique among others, alongside sexual restraint and simplicity of life, for training the soul to want what body and sense cannot supply.
The tension between these two arguments is real and worth dwelling on, since it says something about the limits of Porphyry's ethical consistency more broadly. An argument from justice implies that killing animals is wrong regardless of who does it or why, a claim about what is owed to the animal itself. An argument from spiritual discipline implies only that the philosopher, specifically, gains something by abstaining, which leaves open whether anyone else has done wrong by eating meat at all. Porphyry does not fully resolve which of these is doing the real work, and the strain shows elsewhere in his corpus. In works composed for a different purpose, notably his Philosophy from the Oracles and his Letter to Anebo, he accepts animal sacrifice and does not object to it on principle, treating it as a legitimate part of traditional religious practice even while On Abstinence condemns the killing of animals for food. Read together, these texts suggest a thinker who held his rational, justice based ethics and his inherited reverence for ancestral cult in separate compartments, unwilling or unable to bring the two fully into line.
Whatever its internal strain, the justice based argument in On Abstinence has proven to be Porphyry's most durable philosophical legacy outside the history of logic. By insisting that rationality, not species membership, is what generates a claim to just treatment, he anticipated a line of reasoning that would resurface, transformed, in later debates about the moral status of animals, long after the metaphysical apparatus of Neoplatonism that originally housed it had ceased to persuade anyone.