E3P3D
Demonstration — Part III
Latin
Primum quod mentis essentiam constituit, nihil aliud est quam idea corporis actu existentis (per propositiones 11 et 13 partis II) quæ (per propositionem 15 partis II) ex multis aliis componitur quarum quædam (per corollarium propositionis 38 partis II) sunt adæquatæ, quædam autem inadæquatæ (per corollarium propositionis 29 partis II). Quicquid ergo ex mentis natura sequitur et cujus mens causa est proxima per quam id debet intelligi, necessario ex idea adæquata vel inadæquata sequi debet. At quatenus mens (per propositionem 1 hujus) ideas habet inadæquatas eatenus necessario patitur; ergo mentis actiones ex solis ideis adæquatis sequuntur et mens propterea tantum patitur quia ideas habet inadæquatas. Q.E.D.
English (Elwes 1883)
The first element, which constitutes the essence of the mind, is nothing else but the idea of the actually existent body (II. xi. and xiii.), which (II. xv.) is compounded of many other ideas, whereof some are adequate and some inadequate (II. xxix. Coroll., II. xxxviii. Coroll.). Whatsoever therefore follows from the nature of mind, and has mind for its proximate cause, through which it must be understood, must necessarily follow either from an adequate or from an inadequate idea. But in so far as the mind (III. i.) has inadequate ideas, it is necessarily passive: wherefore the activities of the mind follow solely from adequate ideas, and accordingly the mind is only passive in so far as it has inadequate ideas. Q.E.D.
Modern English
The primary element constituting the essence of the mind is nothing other than the idea of the actually existing body (E2P11), and this idea is composed of many others (E2P15), of which some are adequate (E2P38C) and some inadequate (E2P29C). Whatever follows from the nature of the mind and has the mind as its proximate cause, through which it must be understood, must therefore follow either from an adequate or from an inadequate idea. But insofar as the mind has inadequate ideas, it necessarily undergoes passions (E3P1). Therefore the activities of the mind follow solely from adequate ideas, and the mind is passive only because it has inadequate ideas. Q.E.D.