The existence of intelligent psychopaths, who can understand true moral propositions and yet feel utterly unmotivated to act in accordance with such propositions, have been used to argue that motivational externalism is true.

True.

Explanation:

Motivational externalism is a term used in moral psychology to state that there is no link between moral beliefs and the motivation of individuals to act on them. According to this, psychology states that for a person to do a right and correct action, he needs to feel like doing it, regardless of whether there is a moral belief that supports that action or not. In this case, psychologists use intelligent psychopaths as an example of how motivational externalism works, because intelligent psychopaths do not do good actions because they do not have the will to do them, even if there is a moral belief that influences them to do so.