Ronald Dworkin introduces a tripartite classification into political theories viz, duty-based, goal-based, and right-based theories. J. L. Mackie extends this classification into moral theores. He argues that in addition to duty-based moral theories (e.g., Kant`s theory) and goal-based moral theories (e.g., Utilitarianism), a right-based moral theory is both conceptually possible and morally more desirable. This paper first attempts to analyze the characteristics of Mackie`s right-based moral theory in particular, and any right-based moral theory in general. The present author then contends that there are three major weaknesses of such theories: (1)They over-simplify the relation between duties and rights; (2)they fail to provide adequate guidance to moral life; (3)they cannot account for the true moral significance of supererogation and virtue. Accordingly, the present author agrees that a right-based moral theory is morally truncated and impoverished. It captures only a minimalist ethics. This is because there is a two-fold fundamental error of a right based moral theory, viz., it misplaces the moral subject, and it captures the point or object of morality only partially. The rejection of a right-based moral theory does not imply a rejection of rights. On the contrary, this paper continues to argue for the importance of rights in moral life, and the priority of rights over duties in some cases. In other words, though rights cannot furnish the sufficient basis of morality, it does provide its necessary basis.