DEFINITION OF REACTION OR SUFFERING. 21. How may we define the fact of "reaction"? We do not approve of the definition that it is the passing of the actualization from one being into another, if its receiver appropriate it. Shall we say that a (being) reacts when there is no actualization, but only an effective experience? But is it not possible that the being that reacts becomes better; while, on the contrary, the one who acts, loses? A (being) may also act in an evil manner, and exercise on another a harmful influence; and the actualization may be shameful, and the affective experience be honorable. What distinction shall we then establish (between action and reaction)? Shall we say that an action is to cause (an actualization) to pass from self into others, and that reaction is to receive in oneself (an action) from someone else? But then what about the (actualizations) produced in oneself which do not pass into others, such as thought and opinion? One can even excite oneself by a reflection or opinion of emotive value, without this emotion having been aroused by anybody else. We shall therefore define an action as a spontaneous movement, whether this movement remain in the being who produces it, or whether it pass into somebody else. What then are the faculty of desire, and desire in general? If desire be excited by the desired thing (it is an experience, or passion), even if we should not take into consideration the cause of its excitement, and even if we only noticed that it arose later than the object; for this desire does not differ from an impression or an impulsion. Shall we then, among desires, distinguish actions when they proceed from intelligence, and experiences when they invoke and draw (on the soul), so that the being be less passive by what it receives from others, than by what it receives from itself? Doubtless a being can act upon itself. (We can then define) an affective experience, and a being's experience, as follows. They consist of undergoing, without any contribution from oneself, a modification which does not contribute to "being," and which, on the contrary, alters, or at least, does not improve.