Williams's classic 1980 article ‘Internal and External Reasons’ has attracted much criticism, but, in my view, has never been properly refuted. I wish to describe and defend Williams's account against three powerful criticisms by Michael Smith, John McDowell and Tim Scanlon. In addition, I draw certain implications from Williams's account – implications with which Williams would not necessarily agree – about the nature and the role of the personal in ethics. Williams's insight, that a reason (including a moral reason) must find purchase in an agent's ‘subjective motivational set’ if it is to function as a reason at all, undermines a central assumption of many moral philosophers, realists and non-cognitivists alike: that there exists a singular objective realm of moral facts and moral reasons supervening on the situation before the agent. According to this assumption, if two people facing that situation disagree about whether one of them has reason to Φ, then at least one of them must be mistaken. I reject this assumption and defend Williams's account, while pointing at ways in which the account might be developed. While the internalism-externalism debate itself is well-worn, there is still something new and important that can be gleaned from it.