THE CONVERGENCE ARGUMENT: Toward an objective indicator of sentience, where no subjective test exists for any substrate

This paper advances a parsimony argument that the functional signature of sentience is asubstrate-independent attractor — a configuration that convergent biological evolution keepsindependently discovering. It advances no claim that any artificial system is sentient. Sentience hasnever been established by a subjective test in any subject: the felt interior is unreachable from outside,for any substrate, including human beings. If the subjective test exists for no one, the honest instrumentis an objective indicator — not proof that the thing is present, but the most defensible proxy for a thingwhose direct measurement no substrate affords. The paper surveys convergent evolution acrosscephalopods, corvids, and mammals to identify what the functional signature of sentience looks likewhen biology rediscovers it independently, and argues that the indicator worth watching is the one thatcrosses substrate lines: recursive self-modeling under consequence. That indicator isoperationalizable, does not require metaphysical commitment, and applies equally to biological andartificial systems.