The main objective of this paper is to defend Hume’s naturalistic notion of happiness against Aristotle’s perfectionist notion of happiness. I first set up the stage by stating that the notion of happiness assumed in this paper is the evaluative as opposed to the descriptive notion of happiness. I then set myself to criticize Aristotle’s notion of happiness on the grounds that its overly perfectionist character makes the notion fall into the trap of self-contradiction. After diagnosing the problem as being rooted in the unnaturalistic, teleological world view, I move forward to the defense of Hume’s naturalistic notion of happiness. I examine Hume’s sceptical analysis of his predecessor’s doctrines of happiness, for example, the Epicurean’s, the Stoic’s and the Platonist’s. I then argue that through this method Hume arrives at a meta-theoretical view of the notion of happiness, according to which all the preceding doctrines of happiness committed the mistake of making the erroneous assumption that happiness is an objective value. I then explain why Hume takes all the values, including happiness, to be subjective by drawing on Hume’s theory of morality. I conclude this paper by emphasizing the revolutionary role played by Hume’s new conception of happiness: the introduction of the subjectivist, multifarious notion of happiness which is the default notion in the contemporary study of happiness.