The first investigation relating to society, that concerned with causality, would be directed to solving the problem of the _nature_ of society. Many definitions have been given of this up to the present: and none of them can be said to be generally accepted, or even to claim wide support. Stammler indeed, rejects, after criticism, the definitions of Spencer or Rümelin, which appear to him to be the most important and to be representative of all the others. Society is not an _organism_ (Spencer), nor is it merely something opposed to _legalised society_ (Rümelin): Society, says Stammler, is '_life lived by men in common, subject to rules which are externally binding_.' These rules must be understood in a very wide sense, as all those which bind men living together to something which is satisfied by outward performance. They are divided, however, into two large classes: rules properly speaking _legal_, and rules of _convention_. The second class includes the precepts of propriety and of custom, the code of knightly honour, and so on. The distinctive test lies in the fact that the latter class are merely _hypothetical_, while the former are imposed without being desired by those subjected to them. The whole assemblage of rules, legal and conventional, Stammler calls social _form_. Under these rules, obeying them, limiting them and even breaking them men act in order to satisfy their desires; in this, and in this alone, human life consists. The assemblage of concrete facts which men produce when working together in society, _i.e._, under the assumption of social rules, Stammler calls _social matter_, or _social economics_. Rules, and actions under rules; these are the two elements of which every social datum consists. If the rules were lacking, we should be outside society; we should be animals or gods, as says the old proverb: if the actions were lacking there would remain only an empty form, built up hypothetically by thought, and no portion of which was actually real. Thus social life appears as a single fact: to separate its two constituent factors means either to destroy it, or to reduce it to empty form. The law governing changes within society cannot be found in something which is extra social; not in technique and discovery, nor in the workings of supposed natural laws, nor in the influence of great men, of mysterious racial and national spirit; but it must be sought in the very centre of the social fact itself. Hence it is wrong to speak of a causal bond between law and economics or vice versa: the relation between law and economics is that between the rule and the things ruled, not one of cause and effect. The determining cause of social movements and changes is then ultimately to be found in the actual working out of social rules, which precede such changes. This concrete working out, these actions accomplished under rules, may produce (1) social mutations which are entirely