In the same way the normal state of feeling is the succession of pleasures, troubles, desires, whims, etc., which in their temperate form, and often dulled by repetition, constitute the prosaic round of ordinary life. At a given moment some circumstance causes a shock; that is emotion. Some tendency annihilates all the others, momentarily confiscating the whole activity to its profit; that is the equivalent of attention. Usually this passage of movements in a single direction is not enduring; but if, instead of disappearing, the emotion remains fixed, or repeats itself incessantly, always the same, with the slight modifications involved in passing from the acute to the chronic stage—that is passion, which is permanent emotion. In spite of apparent eclipses, it is always ready to appear, absolute and tyrannical.
Concerning the origin of passion, moralists and novelists have remarked that it comes into being in two different ways—by a thunderbolt or by “crystallisation,” by sudden action or by slow actions. This double origin denotes predominance either of the affective life or of the intellectual life. When passion is born suddenly it issues directly from emotion itself and retains a certain violence of nature, so much at least as its metamorphosis into a permanent disposition admits. In the other case the initiative is taken by the intellectual states (images, ideas), and the passion is slowly constituted as the result of association which itself is only an effect, for it obeys a latent influence, a hidden factor, an unconscious activity only revealed by its work. Representations only attract each other and associate by reason of their affective similitude, of the emotional tone which is common to them, and by successive additions these little streams form a river. This form of passion, on account of its origin, has less ardour and more tenacity.
After distinguishing passion from emotion, it is still necessary to separate it from insanity, its other neighbour. Certain authors have at once classed all passions with insanity; I cannot accept this proposition. It may suit the moralist, by no means the psychologist. But the task of separation is very delicate, and cannot be attempted in this Introduction. The distinction between the normal and the morbid, always difficult, is especially so in the case of the psychology of the feelings. I shall endeavour elsewhere (Part I., Chap. iv.) to find the indications which enable us to establish this separation legitimately, and the task which we now put aside in its general form will come before us later on in the case of each particular emotion.
PART I.
GENERAL PSYCHOLOGY.
CHAPTER I.
PHYSICAL PAIN.
Its anatomical and physiological conditions; pain nerves, transmission to the centres—Modifications of the organism accompanying physical pain: circulation, respiration, nutrition, movements—Are they the effects of paint?—Pain is only a sign—The analgesias: unconsciousness of pain and intellectual consciousness—Retardation of pain after sensation—Hyperalgesia—Nature of pain: theory that it is a sensation; theory that it is a quality of sensation—Pain may result from the quality or the intensity of the stimulus—Hypotheses regarding its ultimate cause: it depends on a form of movement, a chemical modification.
Many definitions of pain have, very unnecessarily, been offered. Some are even tautological, others imply a hypothesis as to its nature by relating it to strong stimulations.[[11]] Let us regard it as an internal state which every one knows by experience, and of which consciousness reveals innumerable modes, but which by its generality and its multiplicity of aspect escapes definition.
In its primitive form pain is always physical, that is to say, connected with external or internal sensations. Sufficiently precise as regards superficial parts of the body, especially the skin, its localisation is vaguer when it is seated in the deeper parts, the viscera, the instruments of organic life. In the last case, when the pain is of internal and non-peripheral origin, coming from the great sympathetic or the related vagus nerve, it is accompanied by a state of anxiety, of depression, or of anguish, which we shall often encounter, and which frequently causes it to be said that “it seems to the patient that the workings of nature within him are suspended.” For the present, without distinguishing between these two origins, external and internal, we will study the objective characters of physical pain taken in general: first its anatomical and physiological conditions, then the bodily modifications which accompany it and in popular language are called its effects.
I.
The transmission of painful impressions from the periphery to the cortical centres is far from being determined in all the stages of its course.