Empirical pluralism and value pluralism

A great many discussions of pluralism in many disciplines focus not on ‘value pluralism’ as Isaiah Berlin understood it, but on empirical claims that there are a lot, or at any rate a number, of things of various sorts. This is obviously true, and any approach to ethics and political philosophy must take account of empirical pluralities. Accounts of justice have, for example, to assume that a plurality of people will be subject to its demands: solipsists don't have to worry about justice. Early modern writers often link the fact that there are many subjects of justice to competition for scarce resources: Locke, Hume and Kant all saw the fact that many share a finite earth as among the basic circumstances of justice.

A second range of empirical claims about pluralities focuses not on the plurality of subjects of justice, but on their varying conceptions of the world and their varying ethical and political views. Empirical evidence that people hold many different moral and political views was of great importance in early modern discussions of toleration and free speech. However, they acquired wider importance in political philosophy in the twentieth century, both through Isaiah Berlin's writings, and because John Rawls and others later persistently emphasised that pluralism of beliefs and outlooks is ineradicable. Rawls held that ‘the fact of reasonable pluralism’ is a ‘permanent feature of democratic societies’, whose ‘citizens affirm irreconcilable and incommensurable conceptions of the good’. He concluded that while people whose conceptions of the good differ can reach agreement on a conception of justice, normative justification cannot reach beyond matters of justice.

Isaiah Berlin was mainly concerned not with the fact that people hold a plurality of beliefs and values, but with the bearing that this has on attempts to justify substantive moral and political claims, including liberal claims, and thereby also claims about human rights. However, unlike Rawls, Berlin does not think that reasonable agreement among fellow citizens can justify principles of justice.

Towards the end of his life he noted that:

The distinction between ‘value pluralism’ and ‘value monism’ was a lasting feature of Berlin's thought, and while the phrase ‘value monism’ is not now much used, …