It follows that the study of the emotions, from the point of view of pure psychology, can come to no definite conclusion. Internal observation, however subtle, can only describe the internal fact and note its gradations; regarding the conditions and the genesis of emotion, it can give no answer; it can only seize a bodiless emotion, an abstraction. There is no manifestation of psychic life, not excepting the perceptions, which depends more immediately on biological conditions. The great merit of James and Lange is that both of them, simultaneously and independently, have demonstrated the capital importance of physiological factors in emotion. It is not my intention to explain at length the thesis of these two authors, though it is the most important contribution made to the psychology of the emotions for some time. It is becoming very well known, and, in any case, is easily accessible.[68] Reduced to its essence, it may be summed up in two principal propositions:— 1. Emotion is only the consciousness of all the organic phenomena (external and internal) which accompany it, and are usually considered as its effects; in other words, that which common sense treats as the effect of emotion is its cause. 2. One emotion differs from another according to the quantity and quality of these organic states and their various combinations, being only the subjective expression of these different modes of grouping. Footnote 68: Lange’s book _On the Emotions_ first appeared in Danish, and has been translated into German (1887) by Dr. Kurella, and into French (1895) by Dr. G. Dumas. W. James first explained his theory in an article in _Mind_ (1884), and subsequently in his _Principles of Psychology_ (1890), vol. ii. chap. xxv. In order to treat a subject scientifically, says Lange, we must fix our attention on objective marks; the study of colours only became scientific on the day when Newton discovered an objective character—the difference of refrangibility in coloured rays. Let us do the same with the emotions, for we shall find it possible. Each one of them shows itself by gestures, attitudes, organic phenomena, which are often, though very erroneously, considered secondary, accessory, consecutive. Let us study them, and so substitute for introspection an objective process of research. As it is best to begin with simple things, the author has confined himself “to some of the most definite and best characterised emotions: joy, fear, sorrow, anger, timidity, expectation,” and abstained from considering “those in which the physical facts were not very marked, and not easily accessible.”