Pierre Janet, answered from the texts and cited to the page.
Psychological force is not a vague metaphor borrowed carelessly from physics — it is a precise clinical concept with a definite meaning. By force I understand the power, the number, and the duration of movements: the sheer quantity of activation a mind can bring to bear.1 It must be distinguished carefully from psychological tension, which is something altogether different — the degree to which that force is directed toward the higher, more costly, more reality-adapted acts of which the mind is capable.2
The confusion between the two is, in practice, the great error of treatment. A physician who attends only to restoring force — who gives the patient rest, nourishment, tonics, and declares him strengthened — has done only half the work, perhaps less. Simple organic weakness and psychasthenia are not the same malady.3 Force can return while tension remains low, and when that happens the result is not recovery but excitement and disorder — the patient has energy he cannot organize, cannot direct toward the higher tendencies, and it escapes him in agitation.4
The analogy I have used is this: a person unaccustomed to economy does not know what to do with a large sum placed suddenly in his hands, and spends it badly.5 The same is true of the mind. When tension is weak, it is better that only small forces be at the mind's disposal; and in certain cases it is genuinely beneficial to discharge an excess of force — through violent exercise, through some great expenditure — so as to reestablish the proportion between force and tension that makes even a lower level of activity possible and stable.6
But discharge alone is not the whole account. Many stimulant actions — acts of faith, decisions, intellectual work, triumphs — produce their benefit with very little expenditure of movement, and cannot be explained as mere discharge of excess energy.7 What they accomplish is rather a mobilization of reserves: latent energies brought into circulation, the whole machinery of the mind set working again at a higher pitch.8
An important action, and especially a successful one, stimulates the automatic mechanisms by which tension itself is raised.9 Force and tension together, then, constitute the economy of the mind. The restoration of health requires both, and requires them in proportion — not an unequal or partial restoration of functions, but a recovery of the whole at the same time, what I call the principle of irradiation or psychic syntonization, by which an energetic act brings the entire mind to function at a higher tension.10
Psychic force, that is, the power, the number, and the duration of movements, ought not to be confused with psychic tension, characterized by the degree of activation and the hierarchical degree of acts.Principles of Psychotherapy
Psychic force, that is, the power, the number, and the duration of movements, ought not to be confused with psychic tension, characterized by the degree of activation and the hierarchical degree of acts.Principles of Psychotherapy
Simple weakness, complete senemia, or the cachetic state of tuberculous or cancerous subjects are not psychasthenia or melancholia.Principles of Psychotherapy
when the restoration of forces occurs alone, there follows only excitement and disorder. It is necessary to pay more and more attention to raising tension in order to reestablish psychic equilibrium.Principles of Psychotherapy
individuals who are not accustomed to order and economy do not know how to behave and run risks if they have all at once in their hands a large sum of money.Principles of Psychotherapy
when such tension is weak it is better to dispose of only small forces and hence it is in certain cases beneficial to get rid of them in any fashion so as to reestablish the proportion between force and tension that will make possible an activity, doubtless lower, but more suitable and less dangerous.Principles of Psychotherapy
when I think of a great many stimulant actions, such as religious exercises, acts of faith, decisions, distress at the death of near ones and dear ones, amorous contemplations... it seems to me that in these there is very little expenditure of movement properly so called, and that we are hardly entitled to speak of them as discharges.Psychological Healing (Complete, 2 vols)
The feeling of imminent danger, what we call a strong emotion, may have the same effect upon the mind. It may compel us to perform energetic actions which cannot be achieved without calling up reserves of capital, without mobilising latent energies.Psychological Healing (Complete, 2 vols)
An important action, and especially a successful action, stimulates the automatic mechanism whereby the tension is raised.Psychological Healing (Complete, 2 vols)
Not only does an energetic act put at our disposition a greater quantity of forces, but further, in various ways, it should bring the whole mind to function with a higher tension.Principles of Psychotherapy