Historically, moral consideration has progressively expanded to include more beings. The expansion of moral concern to include more animal species represents one of the most significant ethical developments of our time.
The moral circle - the set of beings whose interests we consider morally relevant - has expanded throughout human history from immediate family to tribe to nation to humanity and, increasingly, to sentient animals. This expansion is not arbitrary; it is driven by understanding that the capacity for suffering, not species membership, is the morally relevant characteristic. Recognising that farm animals, fish, and potentially invertebrates have interests that matter creates moral obligations that our food systems, policy, and culture are slowly beginning to reflect. The trajectory is toward greater inclusion, though the pace remains inadequate given the scale of current suffering.