Professor Stammler remarks how in the propositions employed by the believers in historical materialism: '_the economic factor dominates the other factors of social life_,' '_the economic factor is fundamental and the others are dependent_,' and the like, the concept economic has never been defined. He is justified in making this remark, and in attaching the greatest importance to it, if he regards and interprets those propositions as assertions of _laws_, as strict propositions of social science. To use as essential in statements of this kind, a concept which could neither be defined nor explained, and which therefore remained a mere word, would indeed be somewhat odd. But his remark is entirely irrelevant when these propositions are understood as: 'summaries of empirical observations, by the help of which concrete social facts may be explained.' I do not think that any sensible person has ever expected to find in those expressions an accurate and philosophical definition of concepts; yet all sensible people readily understand to what class of facts they refer. The word _economic_ here, as in ordinary language, corresponds, not to a concept, but to a _group_ of rather diverse representations, some of which are not even qualitative in content, but quantitative. When it is asserted, that in interpreting history we must look chiefly at the _economic factors_, we think at once of technical conditions, of the distribution of wealth, of classes and sub-classes bound together by definite common interests, and so on. It is true these different representations cannot be reduced to a single concept, but no matter, there is no question of that: here we are in an entirely different _sphere_ from that in which abstract questions are discussed.