How did the Pythagorean belief in reincarnation support opposition to animal slaughter?

The Pythagorean opposition to animal slaughter was rooted in the belief in the transmigration of souls, which held that after death, a human soul could take up residence in the body of an animal.12

Because of this cycle of rebirth, Pythagoreans developed the principle of the "kinship of all beings," suggesting that all living things share a fundamental connection. Consequently, they viewed animals as potential vessels for human souls, making the act of slaughtering and consuming them morally problematic. This belief system led the school to advocate for vegetarianism as a way to respect the interests of other living beings. While other philosophical traditions, such as those influenced by the Stoics, later established hierarchical views that placed humans above animals, the Pythagorean perspective remained a significant early challenge to the practice of animal sacrifice and slaughter in the ancient world.3412