We have just shown that the so-called higher forms of emotion do not escape from the necessity of physiological conditions; but there is yet another question, still in obscurity and suspense, which, by reason of its importance, ought to be elucidated. It is this: Why have certain internal or external states, certain images, certain ideas, the privilege of exciting certain organic and motor states, and, in consequence, emotion? How is this connection, this _nexus_, established? for experience teaches us that it is not necessary: in the same individual the same perception or idea may awaken an emotion, whereas in another case it may produce nothing. In other words, there are perceptions, images, and concepts which remain purely intellectual states without affective accompaniment, at least with none accessible to consciousness. There are others which are immediately enveloped and, as it were, submerged in the emotion which they produce. Let us note that the question comes before us, whatever opinion we may adopt as to the genesis of emotion. As usually accepted, the order is this: intellectual state, affective state, organic states. According to the physiological hypothesis, the order is as follows: intellectual state, organic states, affective state. Passing from one thesis to the other, the problem is subject to but one variation: Why is a certain intellectual state sometimes coupled with an intellectual state, and sometimes not? This is on the first hypothesis. Why is a certain intellectual state sometimes accompanied by organic and motor modifications, sometimes not? This is on the second hypothesis. The answer is the same in both cases: the intellectual state is accompanied by an affective state whenever there is a direct relation with the conditions of existence, natural or social, of the individual. In order to justify this proposition we must examine in succession these two forms of the conditions of existence. 1st Period.—_Sensations or images connected with the natural conditions of existence._