to provide the essential conceptual means for the analysis of real societies, i.e. of concrete social formations.Although basic to his writings, the distinction between mode of production and social formation does not come sharply to the surface in Marx's work nor is his usage of its terms entirely consistent. It is essential, however, that we pursue further their definition by reference to their contextual meaning and with the help of subsequent Marxist exegeses on the matter. It should, then, first of all be understood that Marx's historical investigations took place at a high level of abstraction; not only his overall theorjetical___3ynthesis in the 1859 Preface and elsewhere, but, also, his more specific historical writings as well as his detailed analysis of capitalism dealt with very large historical entities. In them the concept of mode of production was intended as the theoretical representation of certain essential features abstracted from a given series of societies, of concrete social formations, which, in spite of their motley diversity of form, were seen as being held in common by precisely their dominant manner of production.Thus, although abstract, the concept of mode of production is not arbitrary; it is constructed abstractly for the purpose of understanding specific empirical realities. Marx himself emphasised the abstract level. at which he operated by pointing out that in the theoretical analysis in which he was engaged it was usually always assumed that the actual conditions correspond to their conception, or, what is the same, that actual conditions are represented only to the extent that they are typical of their own general case ECapital 111:1 43].Accordingly, in his study of capitalism, for instance, he bore in mind this intrinsic limitation of his analysis; as he characteristically puts it, "in theory it is assumed that the laws of capitalist production operate in their pure form [but -PL] in reality there exists only approximation" Cibid:175].The concept of mode of production was not, therefore, intended as an all-encompassing representation of every aspect of production of a particular society; if that had been the case, Marx would have found himself in the inextricable position of having to 'pigeon-hole', so to * \£* ^_ differentiated by their determinate relations of production] It should be pointed out, however, that, although the principle for the differentiation of modes of production is generally provided by the nature of the production relations characteristic of each one of them, it is not always the same aspect of those relations that serves as the operative criterion