The Instrumental and Deliberative versions of the Present-aim Theory share two distinct claims—that … — Derek Parfit

The Instrumental and Deliberative versions of the Present-aim Theory share two distinct claims—that reasons are determined by what best fulfils present (actual or ideally informed) desires, and that no desires are intrinsically irrational or rationally required—but these claims can be separated, and rejecting the second while accepting a qualified form of the first yields the Critical Present-aim Theory.

By Derek Parfit, from Les raisons et les personnes

Key Arguments

Parfit notes that 'The Instrumental and Deliberative versions, which are widely believed, make two claims: (1) What each person has most reason to do is what would best fulfil the desires that, at the time of acting, he either has or would have if he knew the facts and was thinking clearly. (2) Desires cannot be intrinsically irrational, or rationally required.'
He stresses that 'These are quite different claims.', indicating they are logically independent.
He then proposes a combination that underpins CP: 'We could reject (2) and accept a qualified version of (1). We would then be accepting the Critical version of P.'
This shows that CP preserves the core present‑aim orientation of P (reasons depend on current or idealised present desires) while introducing a substantive, content‑based critical dimension regarding which desires are rationally acceptable or required.

Source Quotes

If we believe that there can be such desires, we should move from the Deliberative to the Critical version of the Present-aim Theory This theory has been strangely neglected. The Instrumental and Deliberative versions, which are widely believed, make two claims: (1) What each person has most reason to do is what would best fulfil the desires that, at the time of acting, he either has or would have if he knew the facts and was thinking clearly. (2) Desires cannot be intrinsically irrational, or rationally required.

The Instrumental and Deliberative versions, which are widely believed, make two claims: (1) What each person has most reason to do is what would best fulfil the desires that, at the time of acting, he either has or would have if he knew the facts and was thinking clearly. (2) Desires cannot be intrinsically irrational, or rationally required. These are quite different claims.

(2) Desires cannot be intrinsically irrational, or rationally required. These are quite different claims. We could reject (2) and accept a qualified version of (1).

These are quite different claims. We could reject (2) and accept a qualified version of (1). We would then be accepting the Critical version of P. This claims CP: Some desires are intrinsically irrational.

Key Concepts

The Instrumental and Deliberative versions, which are widely believed, make two claims:
(1) What each person has most reason to do is what would best fulfil the desires that, at the time of acting, he either has or would have if he knew the facts and was thinking clearly.
(2) Desires cannot be intrinsically irrational, or rationally required.
These are quite different claims.
We could reject (2) and accept a qualified version of (1). We would then be accepting the Critical version of P.

Context

In Section 45, immediately after criticising the Deliberative Theory, Parfit analyses the shared structure of the first two versions of P and uses this to motivate the shift to CP.