E3P58D
Demonstration — Part III
Latin
Cum mens se ipsam suamque agendi potentiam concipit, lætatur (per propositionem 53 hujus) : mens autem se ipsam necessario contemplatur quando veram sive adæquatam ideam concipit (per propositionem 43 partis II). At mens quasdam ideas adæquatas concipit (per scholium II propositionis 40 partis II) : ergo eatenus etiam lætatur quatenus ideas adæquatas concipit hoc est (per propositionem 1 hujus) quatenus agit. Deinde mens tam quatenus claras et distinctas quam quatenus confusas habet ideas, in suo esse perseverare conatur (per propositionem 9 hujus) : at per conatum cupiditatem intelligimus (per ejusdem scholium); ergo cupiditas ad nos refertur etiam quatenus intelligimus sive (per propositionem 1 hujus) quatenus agimus. Q.E.D.
English (Elwes 1883)
When the mind conceives itself and its power of activity, it feels pleasure (III. liii.): now the mind necessarily contemplates itself, when it conceives a true or adequate idea (II. xliii.). But the mind does conceive certain adequate ideas (II. xl. note 2.). Therefore it feels pleasure in so far as it conceives adequate ideas; that is, in so far as it is active (III. i.). Again, the mind, both in so far as it has clear and distinct ideas, and in so far as it has confused ideas, endeavours to persist in its own being (III. ix.); but by such an endeavour we mean desire (by the note to the same Prop.); therefore, desire is also attributable to us, in so far as we understand, or (III. i.) in so far as we are active. Q.E.D.
Modern English
When the mind conceives itself and its power of acting, it feels joy (E3P53). Now the mind necessarily contemplates itself whenever it conceives a true or adequate idea (E2P43). The mind does conceive some adequate ideas (E2P40S2). Therefore it also feels joy insofar as it conceives adequate ideas, that is (E3P1), insofar as it acts. Again, the mind strives to persevere in its being both insofar as it has clear and distinct ideas and insofar as it has confused ideas (E3P9); and by this striving we understand desire (E3P9). Therefore desire is also referred to us insofar as we understand, or (E3P1) insofar as we act. Q.E.D.