But hitherto history has shown us only societies which, in addition to the enjoyment of goods not increasable by labour, have satisfied their needs by labour. Hence this equivalence between value and labour has hitherto had and will continue for an indefinite time to have, a conformity with facts; but, of what kind is this conformity? Having ruled out (1) that it is a question of a moral ideal, and (2) that it is a question of scientific law; and having nevertheless concluded that this equivalence is a _fact_ (which Marx uses as a type), we are obliged to say, as the only alternative, that _it is a fact, but a fact which exists in the midst of other facts; i.e. a fact that appears to us empirically as opposed, limited, distorted by other facts_, almost like a force amongst other forces, which produces a resultant different from what it would produce if the other forces ceased to act. _It is not a completely dominant fact but neither is it non-existent and merely imaginary._[24] It is still necessary to remark that in the course of history this _fact_ has undergone various alterations, _i.e._, has been more or less obscured; and here it is proper to do justice to Engels' remark in reference to Sombart; that as regards the way in which the latter defines the law of value 'he does not bring out the full importance which this law possesses during the stages of economic development in which it is supreme.' Engels makes a digression into the field of economic history to show that Marx's law of value, _i.e._ the equivalence between value and the labour socially necessary, has been supreme for several thousand years.[25] Supreme is too strong a term; but it is true that the opposed influences of other facts to this law have been fewer in number and less intense under primitive communism and under mediæval and domestic economic conditions, whilst they have reached a maximum in the society based on privately owned capital and more or less free universal competition, _i.e._ in the society which produces almost exclusively _commodities_.[26] Marx, then, in postulating as _typical_ the equivalence between value and labour and in applying it to capitalist society, was, as it were, making a comparison between capitalist society and a part of itself, isolated and raised up to an independent existence: _i.e._ a comparison between capitalist society and economic society as such (but only in so far as it is a working society). In other words, he was studying the social problem of labour and was showing by the test implicitly established by him, _the special way in which this problem is solved in capitalist society_. This is the justification, no longer _formal_ but _real_, of his method.