E4P59D
Demonstration — Part IV
Latin
Ex ratione agere nihil aliud est (per propositionem 3 et definitionem 2 partis III) quam ea agere quæ ex necessitate nostræ naturæ in se sola consideratæ sequuntur. At tristitia eatenus mala est quatenus hanc agendi potentiam minuit vel coercet (per propositionem 41 hujus); ergo ex hoc affectu ad nullam actionem possumus determinari quam non possemus agere si ratione duceremur. Præterea lætitia eatenus mala est quatenus impedit quominus homo ad agendum sit aptus (per propositiones 41 et 43 hujus) atque adeo eatenus etiam ad nullam actionem determinari possumus quam non possemus agere si ratione duceremur. Denique quatenus lætitia bona est eatenus cum ratione convenit (consistit enim in eo quod hominis agendi potentia augetur vel juvatur) nec passio est nisi quatenus hominis agendi potentia non eo usque augetur ut se suasque actiones adæquate concipiat (per propositionem 3 partis III cum ejus scholio). Quare si homo lætitia affectus ad tantam perfectionem duceretur ut se suasque actiones adæquate conciperet, ad easdem actiones ad quas jam ex affectibus qui passiones sunt, determinatur, aptus, imo aptior esset. At omnes affectus ad lætitiam, tristitiam vel cupiditatem referuntur (vide explicationem quartæ affectuum definitionis) et cupiditas (per 1 affectuum definitionem) nihil aliud est quam ipse agendi conatus; ergo ad omnes actiones ad quas ex affectu qui passio est, determinamur, possumus absque eo sola ratione duci. Q.E.D.
English (Elwes 1883)
To act rationally, is nothing else (III. iii. and Def. ii.) but to perform those actions, which follow from the necessity, of our nature considered in itself alone. But pain is bad, in so far as it diminishes or checks the power of action (IV. xli.); wherefore we cannot by pain be determined to any action, which we should be unable to perform under the guidance of reason. Again, pleasure is bad only in so far as it hinders a man's capability for action (IV. xli. xliii.); therefore to this extent we could not be determined by it to any action, which we could not perform under the guidance of reason. Lastly, pleasure, in so far as it is good, is in harmony with reason (for it consists in the fact that a man's capability for action is increased or aided); nor is the mind passive therein, except in so far as a man's power of action is not increased to the extent of affording him an adequate conception of himself and his actions (III. iii., and note).
Wherefore, if a man who is pleasurably affected be brought to such a state of perfection, that he gains an adequate conception of himself and his own actions, he will be equally, nay more, capable of those actions, to which he is determined by emotion wherein the mind is passive. But all emotions are attributable to pleasure, to pain, or to desire (Def. of the Emotions, iv. explanation); and desire (Def. of the Emotions, i.) is nothing else but the attempt to act; therefore, to all actions, &c. Q.E.D.
Another Proof.--A given action is called bad, in so far as it arises from one being affected by hatred or any evil emotion. But no action, considered in itself alone, is either good or bad (as we pointed out in the preface to Pt. IV.), one and the same action being sometimes good, sometimes bad; wherefore to the action which is sometimes bad, or arises from some evil emotion, we may be led by reason (IV. xix.). Q.E.D.
Modern English
To act from reason is nothing other (E3P3) than to do those things that follow from the necessity of our own nature considered in itself alone. Sadness is bad insofar as it diminishes or restrains our power of acting (E4P41); so from this affect we cannot be determined to any action that we could not perform if we were guided by reason. Again, joy is bad only insofar as it prevents a person from being fit to act (E4P41); so to that extent we cannot be determined by it to any action we could not perform under the guidance of reason. As for joy insofar as it is good, it is in accord with reason (for it consists in the fact that a person's power of acting is increased or aided), and it is a passion only insofar as a person's power of acting is not increased to the point where he conceives himself and his actions adequately (E3P3S). Therefore, if a person affected by joy were brought to such perfection that he conceived himself and his actions adequately, he would be equally — indeed more — fit for those same actions to which he is now determined by affects that are passions. All affects, however, refer to joy, sadness, or desire (E3DA4), and desire (E3DA1) is nothing other than the striving to act itself. Therefore we can be determined, by reason alone, to all the actions to which we are determined by an affect that is a passion. Q.E.D.