The argument from moral psychology

The argument from moral psychology is one of the strongest arguments that non-cognitivists use against cognitivism-the metaethical position according to which our moral judgements express beliefs. According to this argument, once we put together the Humean theory of motivation and motivational internalism, we yield the conclusion that cognitivism cannot represent the correct view about the semantic function of moral discourse. I will first attempt to show that a neurological syndrome, called pain asymbolia (a rare condition caused by lesions to the posterior insula that produces complete, thoroughgoing indifference to pain), can be used in order to formulate a persuasive defence of the Humean theory of motivation. After that, I will consider motivational internalism and argue that, without additional empirical evidence, neither internalism nor externalism can provide a plausible explanation of the connection between moral judgements and motivation. In conclusion, I intend to defend the claim that, until more persuasive arguments in favour of internalism are presented, non-cognitivists should not rely on the argument from moral psychology in their attempts to refute cognitivism.