 Consequently, propositions and problems can be, and therefore in some cases should be, elucidated by means of tenets, or opinions: doxai. As there are three sets of propositions, so there are three sets of doxai: physical, ethical, and ‘logical’ (i.e., general). An example of such a diaeresis, or division, of a sub-set which is of fundamental importance for Aristotle is found at the beginning of his Physics. This division pertains to two categories and one predicate of a different sort: the number (category of quantity), nature (category of substance) and motion vs. rest (category of doing and being-affected) of the principles (archai) and elements (stoicheia) posited by Aristotle’s predecessors in the field of natural philosophy. In line with the rule formulated in the Topics names of philosophers are added to some of the doxai. Numerous other examples of this ingredient of the dialectical method are to be found in Aristotle’s writings.