- Your preferences aren’t over world states, but propositions being satisfied
- The propositions are drawn from your unstable, contradictory mental model
- You therefore need to revise the content of your preferences to make them fulfillable
- This requires conceptual revision of the value-propositions
- Therefore you must guide your preference/value-concept revision using ethical ideals
So ethical truth is needed to give instrumental reason any force, which is in turn needed to ground meanings, which are in turn needed to make any assertions. So ethics is needed for truth and argument I.e. theoretical reason.
Maybe relevant to the shifting sands paper about vagueness? Delia Graff