PROP. IV. There is no modification of the body, whereof we cannot form some clear and distinct conception.

Proof.—Properties which are common to all things can only be conceived adequately (II. xxxviii.); therefore (II. xii. and Lemma ii. after II. xiii.) there is no modification of the body, whereof we cannot form some clear and distinct conception. Q.E.D.

Corollary.—Hence it follows that there is no emotion, whereof we cannot form some clear and distinct conception. For an emotion is the idea of a modification of the body (by the general Def. of the Emotions), and must therefore (by the preceding Prop.) involve some clear and distinct conception.

Note.—Seeing that there is nothing which is not followed by an effect (I. xxxvi.), and that we clearly and distinctly understand whatever follows from an idea, which in us is adequate (II. xl.), it follows that everyone has the power of clearly and distinctly understanding himself and his emotions, if not absolutely, at any rate in part, and consequently of bringing it about, that he should become less subject to them. To attain this result, therefore, we must chiefly direct our efforts to acquiring, as far as possible, a clear and distinct knowledge of every emotion, in order that the mind may thus, through emotion, be determined to think of those things which it clearly and distinctly perceives, and wherein it fully acquiesces: and thus that the emotion itself may be separated from the thought of an external cause, and may be associated with true thoughts; whence it will come to pass, not only that love, hatred, &c. will be destroyed (V. ii.), but also that the appetites or desires, which are wont to arise from such emotion, will become incapable of being excessive (IV. lxi.). For it must be especially remarked, that the appetite through which a man is said to be active, and that through which he is said to be passive is one and the same. For instance, we have shown that human nature is so constituted, that everyone desires his fellow—men to live after his own fashion (III. xxxi. note); in a man, who is not guided by reason, this appetite is a passion which is called ambition, and does not greatly differ from pride; whereas in a man, who lives by the dictates of reason, it is an activity or virtue which is called piety (IV. xxxvii. note. i. and second proof). In like manner all appetites or desires are only passions, in so far as they spring from inadequate ideas; the same results are accredited to virtue, when they are aroused or generated by adequate ideas. For all desires, whereby we are determined to any given action, may arise as much from adequate as from inadequate ideas (IV. lix.). Than this remedy for the emotions (to return to the point from which I started), which consists in a true knowledge thereof, nothing more excellent, being within our power, can be devised. For the mind has no other power save that of thinking and of forming adequate ideas, as we have shown above (III. iii.).