  The battle lines in the debate between pluralism and monism are not always clear. In this entry I have outlined some of them, and discussed some of the main arguments. Pluralists need to be clear about whether they are foundational or non-foundational pluralists. Monists must defend their claim that there really is a unitary value. Much of the debate between pluralists and monists has focussed on the issue of whether the complexity of moral choice implies that values really are  plural—a pattern emerges in which the monist claims to be able to explain the appearance of plurality away, and the pluralist insists that the appearance reflects a pluralist reality. Finally, pluralists must explain how comparisons between values are made, or defend the consequence that incommensurability is widespread.  