 There are a number of direct moral criticisms made of strict equality principles: that they unduly restrict freedom, that they do not give best effect to the moral equality of persons, that they conflict with what people deserve, etc. (see the sections on  Libertarian Principles,  and  Desert-Based Principles,  and the entry on  equality).  But the most common criticism is a welfare-based one related to the Pareto efficiency requirement: that everyone can be materially better off if incomes are not strictly equal (Carens 1981). It is this criticism which partly inspired the Difference Principle.