I would say that the orthogonality thesis does not necessarily imply moral non-realism… but some forms of moral non-realism do imply the orthogonality thesis, in which case rejecting the orthogonality thesis would require rejecting at least that particular kind of moral non-realism. This may cause moral non-realists of that variety to equate moral realism and a rejection of the OT.
For example, if you are a moral non-cognitivist, then according to the SEP, you believe that:
when people utter moral sentences they are not typically expressing states of mind which are beliefs or which are cognitive in the way that beliefs are. Rather they are expressing non-cognitive attitudes more similar to desires, approval or disapproval.
This would seem to imply the orthogonality thesis: different agents will have different desires and goals, and if goals have no inherent truth value and moral statements simply reflect our desires and goals, then there is no particular reason to expect agents with a higher intelligence to converge on the same goals/moral beliefs. They’ll just keep their original desires/goals, since no amount of increased intelligence could reveal facts which would cause those desires/goals to change (with the possible exception of cases where increased intelligence reveals a goal to have been logically incoherent).
Non-cognitivism strictly speaking doesn’t imply the orthogonality thesis. For instance, one could consistently hold that increased intelligence leads to a convergence of the relevant non-cognitive attitudes. Admittedly, such a position appears implausible, which might explain the fact (if it is a fact) that non-cognitivists are more prone to accept the orthogonality thesis.
I would say that the orthogonality thesis does not necessarily imply moral non-realism… but some forms of moral non-realism do imply the orthogonality thesis, in which case rejecting the orthogonality thesis would require rejecting at least that particular kind of moral non-realism. This may cause moral non-realists of that variety to equate moral realism and a rejection of the OT.
For example, if you are a moral non-cognitivist, then according to the SEP, you believe that:
This would seem to imply the orthogonality thesis: different agents will have different desires and goals, and if goals have no inherent truth value and moral statements simply reflect our desires and goals, then there is no particular reason to expect agents with a higher intelligence to converge on the same goals/moral beliefs. They’ll just keep their original desires/goals, since no amount of increased intelligence could reveal facts which would cause those desires/goals to change (with the possible exception of cases where increased intelligence reveals a goal to have been logically incoherent).
Non-cognitivism strictly speaking doesn’t imply the orthogonality thesis. For instance, one could consistently hold that increased intelligence leads to a convergence of the relevant non-cognitive attitudes. Admittedly, such a position appears implausible, which might explain the fact (if it is a fact) that non-cognitivists are more prone to accept the orthogonality thesis.