Existence internalism claims that facts about human psychological responsiveness constrain the metaphysics of value in particular ways. Chapter 5 examines whether some form of existence internalism holds for prudential value. It emphasizes the importance of a modal distinction that has been traditionally overlooked. Some facts about personal good are facts about realized good. For example, right now it may be true that X is good for me. Other facts about goodness are facts about what would be good for me in certain possible futures. These are facts about merely possible good. Philosophers should be internalists about realized good. The chapter defends a qualified version of the idea that a necessary constraint on something’s being good for a person at a time is that the thing in question elicits some kind of positive psychological response from the person at that time. However, philosophers should be motivational externalists about merely possible good. Facts about the superior future goodness of an option may ground reasons now to choose it. But we should not expect individuals to always recognize such facts, and so there is no reason to think such facts are always motivating.