Spinoza's Ethics: III.P37 - Feedback Loop for Desire

Cupiditas quæ præ tristitia vel lætitia præque odio vel amore oritur, eo est major quo affectus major est.

Desire which arises on behalf of sadness or joy and on behalf of hatred or love, is the greater as the greater the emotion.

DEMONSTRATIO: Tristitia hominis agendi potentiam (per scholium propositionis 11 hujus) minuit vel coercet hoc est (per propositionem 7 hujus) conatum quo homo in suo esse perseverare conatur, minuit vel coercet adeoque (per propositionem 5 hujus) huic conatui est contraria et quicquid homo tristitia affectus conatur, est tristitiam amovere. At (per tristitiæ definitionem) quo tristitia major est, eo majori parti hominis agendi potentiæ necesse est opponi; ergo quo major tristitia est, eo majore agendi potentia conabitur homo contra tristitiam amovere hoc est (per scholium propositionis 9 hujus) eo majore cupiditate sive appetitu conabitur tristitiam amovere. Deinde quoniam lætitia (per idem scholium propositionis 11 hujus) hominis agendi potentiam auget vel juvat, facile eadem via demonstratur quod homo lætitia affectus nihil aliud cupit quam eandem conservare idque eo majore cupiditate quo lætitia major erit. Denique quoniam odium et amor sunt ipsi tristitiæ vel lætitiæ affectus, sequitur eodem modo quod conatus, appetitus sive cupiditas quæ præ odio vel amore oritur, major erit pro ratione odii et amoris. Q.E.D.

Sadness diminishes the power of acting of a human (by IIIP11S [Good for Body, Good for Mind]) or restrains, that is (by IIIP7 [Efforting]) the efforting by which a human tries to persevere to be in oneself, diminishes or restrains to such a degree (by IIIP5 [Self-Contradiction]) is contrary to this efforting and whatever person with an emotion by sadness attempts is to remove the sadness. But (by the definition of sadness) the greater is the sadness, then the greater part is the necessity of the power of acting to oppose; thus the greater the sadness, the greater by the power of acting will a person try to remove against the sadness that is (by IIIP9S [Awareness of Efforting]) by the greater desire and appetite will one try to remove the sadness. Next since joy (by the same IIIP11S [Good for Body, Good for Mind]) increases or aides the power of a human's acting, it is demonstrated easily in the same way because a person with the emotion of (by) joy desires nothing else than to keep the same and the greater the desire, the greater will be the joy. Finally because love and hate are emotions of sadness and joy themselves, it follows in the same way because efforting, whether as appetite or desire which arises from hatred or love, will be more on behalf of the reason of hatred or love.