  From this understanding of the concept of a practical reason, Williams (on this interpretation) believes he can prove that all ‘external reasons statements’ are false by considering the special case of first personal reasons beliefs: an agent’s beliefs about what considerations are reasons for himself. This argument requires a further assumption: that R is a reason for an agent to do A only if he could, through sound deliberation, come to recognize it as a reason for his doing A.  This assumption seems reasonable given the conceptual premise, that the notion of a ‘reason for action’ is just some notion of an explanation of action. A ‘reason for an agent’ would then plausibly be an explanation for that agent, and it is plausible that what can be an explanation for an agent is restricted to what the agent is able to come to recognize as an explanation.