seek to determine the very various conditions of their genesis, not by way of deduction, but by that of analysis or synthesis based on observation, _i.e._, as far as possible by a genetic method. We have elsewhere spoken of classification and the insurmountable difficulties inherent in it; accordingly, the aim which we propose to ourselves is not, given a composite emotion, to determine its genus and species, but to know _from what primary emotion, and in what manner, it is derived_. Footnote 163: _Traité des Passions_, sec. 69. These natural methods of transition from the simple to the complex seems to me capable of being ranged under three heads: (1) evolution, (2) arrest of development, (3) composition (mixture and combination). These three methods may act separately or conjointly; the more complex emotions are usually the result of their co-operation. We shall examine them in succession. I. The transition _by evolution_, complete or incomplete, is the simplest and most general case. It consists, like all evolution, in the passage from simplicity to complexity, from the undifferentiated to the differentiated, from the lower to the higher. It depends on the intellectual development, and is based on the law of transference already described (Pt. I., chap. xii.), which is its active and unconscious instrument. However feeble the development of the emotions may be in any race or individual it is never entirely wanting (idiots excepted), because the events of national and individual life have always some variety and some changes of aspect, which influence the emotional life. It is convenient to distinguish two cases, according as the evolution takes place in a homogeneous or a heterogeneous form. I. _Evolution in homogeneous form._—The primary emotion remains identical with itself, through the whole course of evolution; it only increases in complexity. Here are some examples:[164] ----- Footnote 164: As all the emotions to be enumerated in this chapter have been already—or are about to be—studied separately, they will only be mentioned briefly, by way of example, and in order to illustrate the work of the mind in the creation of composite forms. -----