I have indicated in passing why a true classification of the emotions—_i.e._, a distribution into orders, genera, species, according to the dominant and subordinate characters—is impossible. Every classification, if not purely empirical, expresses a general theory of affective life, a “system,” and, consequently, a hypothesis. More than this, it can never congratulate itself on having exhausted its matter, for every emotion, simple or compound, admits of innumerable varieties determined by the individual, the race, the epoch, and the course of civilisation; some are extinct, others, again, of recent origin. Lastly, the existence of mixed emotions—which are numerous—is a fatal objection to every attempt at distribution into a linear series. The only track to follow is that of genetic filiation—viz., to state first the simple, primary emotions, then to find out by what mental processes, conscious or unconscious, the composite and derived emotions have arisen from them. We shall attempt to define these in a future chapter.[95] But this work is no longer a classification. Footnote 95: See Part II., chap. vii. CHAPTER XI. THE MEMORY OF FEELINGS. _Can emotional images be revived, spontaneously or voluntarily?—Summary of scattered facts relating to this subject—Inquiry into this question, and method followed—Emotional and gustative images—Internal sensations (hunger, thirst, fatigue, disgust, etc.)—Pleasures and pains; observations—Emotions: three distinct forms of revivability according to observations—Reduction of the images to three groups: revivability direct and easy, indirect and comparatively easy, difficult and sometimes direct, sometimes indirect.—The revivability of a representation is in proportion to its complexity and the motor elements included in it.—Reservations to be made on this last point—Is there such a thing as a real emotional memory?—Two cases: false or abstract, and true or concrete memory—Peculiar characters and differences of each case—Change of the emotional into an intellectual recollection—Emotional amnesia: its practical consequences—There exists a general emotional type and partial emotional types—Confirmatory observations—Comparative revivability of agreeable and disagreeable states—To feel acutely and to recall an acute impression of the feeling are two different operations._ I.