Externalism: It is possible for a person to sincerely hold a moral belief (or make a moral judgment) without feeling any motivation to adhere to that belief/judgment. The claim is not just that the motivation might be trumped by other motivations, it is that it is possible for there to be no motivation at all.

Internalism: It is impossible to sincerely make a moral judgment without being motivated to act in accordance with it, although it may be the case that the motivation is trumped by other countervailing motivations.