E2P5D
Demonstration — Part II
Latin
Patet quidem ex propositione 3 hujus. Ibi enim concludebamus Deum ideam suæ essentiæ et omnium quæ ex ea necessario sequuntur, formare posse ex hoc solo nempe quod Deus est res cogitans et non ex eo quod sit suæ ideæ objectum. Quare esse formale idearum Deum quatenus est res cogitans, pro causa agnoscit. Sed aliter hoc modo demonstratur. Esse formale idearum modus est cogitandi (ut per se notum) hoc est (per corollarium propositionis 25 partis I) modus qui Dei naturam quatenus est res cogitans, certo modo exprimit adeoque (per propositionem 10 partis I) nullius alterius attributi Dei conceptum involvit et consequenter (per axioma 4 partis I) nullius alterius attributi nisi cogitationis est effectus adeoque esse formale idearum Deum quatenus tantum ut res cogitans consideratur etc. Q.E.D.
English (Elwes 1883)
This proposition is evident from Prop. iii. of this Part. We there drew the conclusion, that God can form the idea of his essence, and of all things which follow necessarily therefrom, solely because he is a thinking thing, and not because he is the object of his own idea. Wherefore the actual being of ideas owns for cause God, in so far as he is a thinking thing. It may be differently proved as follows: the actual being of ideas is (obviously) a mode of thought, that is (Part i., Prop. xxv., Coroll.) a mode which expresses in a certain manner the nature of God, in so far as he is a thinking thing, and therefore (Part i., Prop. x.) involves the conception of no other attribute of God, and consequently (by Part i., Ax. iv.) is not the effect of any attribute save thought. Therefore the actual being of ideas owns God as its cause, in so far as he is considered as a thinking thing, &c. Q.E.D.
Modern English
This is evident from E2P3 (E2P3). There we concluded that God can form the idea of his essence and of all things that follow necessarily from it, solely because he is a thinking thing, not because he is the object of his own idea. So the formal being of ideas has God as its cause insofar as he is a thinking thing.
There is also another way to demonstrate this. The formal being of ideas is a mode of thought (E1P25C), that is, (E1P10), a mode that expresses the nature of God insofar as he is a thinking thing, in a certain determinate way. It therefore involves the concept of no other attribute of God (E1P10), and consequently is the effect of no attribute other than thought (E1A4). So the formal being of ideas has God as its cause only insofar as he is considered as a thinking thing, and so on. Q.E.D.