The criterion of moral status
On the axis: Moral circle · a living being
What gives a being moral worth: reason, as Kant held, or the mere capacity to suffer, as Bentham asked? Depending on the threshold chosen, the circle of beings that count opens or narrows.
Justification
If the sole title to enter the calculus is to be able to feel pleasure and pain, then the boundary of moral consideration must follow sentience, not reason or language. Bentham thus turns back both the Cartesian argument of the animal-machine and the one that once excluded the slave: it is not the faculty of reasoning or talking that grounds a claim to consideration, but the capacity to suffer. The conclusion follows from the consistency of the utilitarian criterion itself: consideration extends to every sentient being, placing him in pathocentrism and making him a precursor of the animal cause.
The question is not, Can they reason? nor, Can they talk? but, Can they suffer?An Introduction to the Principles of Morals and Legislation, ch. XVII
An Introduction to the Principles of Morals and Legislation, ch. XVII, §1, footnote (the suffering of animals)
Justification
The holds for all people and all times: the criterion of pleasure and pain is a universal natural fact, and the calculus applies the same way everywhere. Bentham does not relativize morality to cultures nor reduce it to mere convention; this is a naturalistic universalism, grounded in a sentience common to all beings.
An Introduction to the Principles of Morals and Legislation, ch. I-IV (the principle and its measure, universally valid)
Justification
The moral law holds universally for every rational being, independently of cultures and inclinations: this is the most assertive universalism in the tradition. A slight constructivist weight is warranted by autonomy: the law is not discovered in the world, reason gives it to itself.
Groundwork of the Metaphysics of Morals, section II · Critique of Practical Reason
Justification
Deprived of thought and therefore of soul, animals are for Descartes mere automata, the famous beast-machine: they neither feel nor suffer in the proper sense, their cries being only mechanical effects. Moral consideration is thereby restricted to thinking beings alone, a strict anthropocentrism.
Discourse on Method, V · Letter to the Marquess of Newcastle, 23 November 1646
Anchors: Bentham · Kant · Descartes
leads to: Status of norms (metaethics) (Are there moral truths?)