Phil458 Presentation (session 6)

Session 6 ●

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Outline and discuss Pigden’s strategy for dealing with Prior’s counter­examples to No­Ought­From­ Is in ‘Logic and the Autonomy of Ethics’. Is Pigden’s strategy a success? What implications (if any) does Pigden’s paper have for meta­ethics?

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Logical autonomy is an instance of the more general thesis that logic is conservative. The vague conception of the conservativeness of logic is not tenable, as Prior shows, – so if it is true it must be reformulated. Deontic logic and the conservativeness principle conflict, but it is more likely to be deontic logic that should be revised or rejected.

Logical autonomy ●

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“Logical autonomy maintains that moral conclusions cannot be derived from non­moral premises.” logical autonomy is an instance of the more general thesis that logic is conservative. Roughly stated, “logic preserves, but does not extend, truth and content.” –

The conclusion in some sense contains the premises.

the conservativeness principle ●

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But the rough principle of the conservativeness of logic is not tenable Prior's counterexamples are counterexamples not only to logical autonomy but to the conservativeness of logic. Shorter, points out that these sentences are morally trivial, but there is no reason to suspect that all counter examples would be morally trivial.

Conservativeness Re­stated ●

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The most certain way to affirm that any moral conclusion from non­moral premises would be morally trivial is to have a logical principle to uphold that claim. Pigden reformulates the conservativeness principle to do this work. “A predicate or propositional variable cannot occur non­vacuously in the conclusion of a valid inference unless it appears among the premises.”

Inference­relative Vacuity ●

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1. Tea­drinking is common in England. Therefore 2. Either tea­drinking is common in England or all New Zealanders are hedgehogs The occurrence of hedgehog is vacuous relative to the inference; but taken as a premise, the occurrence of hedgehog would be non­vacuous. This escapes Prior's dilemma, and I believe Pigden's proof of this for classical predicate calculus succeeds

Deontic logic ●

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In virtue of the semantics of deontic logic, it is possible for there to be sentences in which ought appears non­vacuously in the conclusion where it does not appear in the premises. There are good reasons for current deontic logic, but I believe the arguments against it are better.

Meta­Ethics ●

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Logical autonomy plays a part in the debate between naturalism and ontological autonomy. Ontological autonomy: “moral judgements, to be true, must answer to a realm of sui generis non­natural properties Naturalism: “though there are moral truths, there are no peculiar or irreducibly moral facts or properties.

Logical autonomy and Meta­Ethics ●

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Logical autonomy follows from ontological autonomy, so if logical autonomy were false, ontological autonomy would be too. But both the truth and falsity of logical autonomy are compatible with naturalism. So, to defend ontological autonomy one must defend logical autonomy, but in defending logical autonomy one does not provide argument against naturalism.