=Emotions compared with Instincts.=--An emotion is a tendency to feel, and an instinct is a tendency to act, characteristically, when in presence of a certain object in the environment. But the emotions also have their bodily 'expression,' which may involve strong muscular activity (as in fear or anger, for example); and it becomes a little hard in many cases to separate the description of the 'emotional' condition from that of the 'instinctive' reaction which one and the same object may provoke. Shall _fear_ be described in the chapter on Instincts or in that on Emotions? Where shall one describe _curiosity_, _emulation_, and the like? The answer is quite arbitrary from the scientific point of view, and practical convenience may decide. As inner mental conditions, emotions are quite indescribable. Description, moreover, would be superfluous, for the reader knows already how they feel. Their relations to the objects which prompt them and to the reactions which they provoke are all that one can put down in a book. Every object that excites an instinct excites an emotion as well. The only distinction one may draw is that the reaction called emotional terminates in the subject's own body, whilst the reaction called instinctive is apt to go farther and enter into practical relations with the exciting object. In both instinct and emotion the mere memory or imagination of the object may suffice to liberate the excitement. One may even get angrier in thinking over one's insult than one was in receiving it; and melt more over a mother who is dead than one ever did when she was living. In the rest of the chapter I shall use the word _object_ of emotion indifferently to mean one which is physically present or one which is merely thought of.