This paper addresses an ongoing debate concerning the dimensionality of Inglehart's (1971, 1977, 1981, 1990) concept of materialism-postmaterialism. According to Inglehart, this concept is unidimensional, distinct from the traditional left-right political belief continuum, and central to explaining the changes taking place in the values of advanced industrial societies. To date, the debate has sought answers in different item sets, factor analytic solutions, and rotations. This paper approaches the problem through psychological models of social values. Materialism-postmaterialism, it is argued, involves a prioritizing of values from two orthogonal value orientations which have grown out of the work of Rokeach (1973): national strength and order and international harmony and equality.