Equal consideration of interests, not equal treatment, is the real principle of equality

Singer's foundational move is distinguishing equal consideration from equal treatment: treating beings equally doesn't mean giving them identical outcomes, but weighing their comparable interests with the same seriousness regardless of who holds them. He illustrates this with a triage scenario — if you have limited morphine after an earthquake and must choose between someone in agony and someone in mild pain, equal consideration favors relieving the greater suffering, not splitting the dose evenly.

This principle, he argues, doesn't depend on beings actually being equal in ability or characteristics — humans plainly differ enormously from one another and from animals in intelligence, strength, and other traits. What equal consideration demands is that an interest, such as avoiding pain, count the same regardless of whose interest it is, since the pain itself is equally undesirable whoever experiences it. This reframing is what allows Singer to extend moral concern to animals without claiming animals and humans are identical in capacities.

Takeaway: equality in ethics isn't about treating everyone the same — it's about refusing to discount someone's suffering just because of who they are.