E4P35D
Demonstration — Part IV
Latin
Quatenus homines affectibus qui passiones sunt, conflictantur, possunt esse natura diversi (per propositionem 33 hujus) et invicem contrarii (per propositionem præcedentem). Sed eatenus homines tantum agere dicuntur quatenus ex ductu rationis vivunt (per propositionem 3 partis III) atque adeo quicquid ex humana natura quatenus ratione definitur, sequitur id (per definitionem 2 partis III) per solam humanam naturam tanquam per proximam suam causam debet intelligi. Sed quia unusquisque ex suæ naturæ legibus id appetit quod bonum et id amovere conatur quod malum esse judicat (per propositionem 19 hujus) et cum præterea id quod ex dictamine rationis bonum aut malum esse judicamus, necessario bonum aut malum sit (per propositionem 41 partis II). Ergo homines quatenus ex ductu rationis vivunt eatenus tantum ea necessario agunt quæ humanæ naturæ et consequenter unicuique homini necessario bona sunt hoc est (per corollarium propositionis 31 hujus) quæ cum natura uniuscujusque hominis conveniunt atque adeo homines etiam inter se quatenus ex ductu rationis vivunt, necessario semper conveniunt. Q.E.D.
English (Elwes 1883)
In so far as men are assailed by emotions that are passions, they can be different in nature (IV. xxxiii.), and at variance one with another. But men are only said to be active, in so far as they act in obedience to reason (III. iii.); therefore, what so ever follows from human nature in so far as it is defined by reason must (III. Def. ii.) be understood solely through human nature as its proximate cause. But, since every man by the laws of his nature desires that which he deems good, and endeavours to remove that which he deems bad (IV. xix.); and further, since that which we, in accordance with reason, deem good or bad, necessarily is good or bad (II. xli.); it follows that men, in so far as they live in obedience to reason, necessarily do only such things as are necessarily good for human nature, and consequently for each individual man (IV. xxxi. Coroll.); in other words, such things as are in harmony with each man's nature. Therefore, men in so far as they live in obedience to reason, necessarily live always in harmony one with another. Q.E.D.
Modern English
In so far as men are driven by affects that are passions, they can differ in nature (E4P33) and be contrary to one another (E4P34). But men are said to act only in so far as they live under the guidance of reason (E3P3), and whatever follows from human nature, in so far as it is defined by reason, must be understood through human nature alone as its proximate cause (E3D2). Since every person by the laws of their nature desires what they judge good and strives to remove what they judge bad (E4P19), and since what we judge good or bad in accordance with reason is necessarily good or bad (E2P41), it follows that men, in so far as they live under the guidance of reason, do only what is necessarily good for human nature and therefore necessarily good for each individual (E4P31C), that is, what agrees with each person's nature. Men who live under the guidance of reason, therefore, necessarily always agree in nature.