 One of the knottiest dimensions of Berlin’s pluralism is the idea of incommensurability, which has led to diverging interpretations. One can make a three-way distinction, between weak incommensurability, moderate incommensurability and radical incommensurability. Weak incommensurability is the view that values cannot be ranked quantitatively, but can be arranged in a qualitative hierarchy that applies consistently in all cases. Berlin goes further than this, but it is not clear whether he presents a moderate or a radical version of incommensurability. The former holds that there is no single, ultimate scale or principle with which to measure values – no moral ‘slide-rule’ (2002b, 216) or universal unit of normative measurement. This view is certainly consistent with all that Berlin wrote from the 1930s onwards. Such a view does not necessarily rule out making judgements between values on a case-by-case basis: just because values can’t be compared or ranked in terms of one master-value or formula, we can’t conclude that it is impossible to compare or deliberate between them at all, as we indeed do in actual cases.