E1P30D
Demonstration — Part I
Latin
Idea vera debet convenire cum suo ideato (per axioma 6) hoc est (ut per se notum) id quod in intellectu objective continetur, debet necessario in natura dari. Atqui in natura (per corollarium I propositionis 14) non nisi una substantia datur nempe Deus nec ullæ aliæ affectiones (per propositionem 15) quam quæ in Deo sunt et quæ (per eandem propositionem) sine Deo nec esse nec concipi possunt; ergo intellectus actu finitus aut actu infinitus Dei attributa Deique affectiones comprehendere debet et nihil aliud. Q.E.D.
English (Elwes 1883)
A true idea must agree with its object (Ax. vi.); in other words (obviously), that which is contained in the intellect in representation must necessarily be granted in nature. But in nature (by Prop. xiv., Coroll. i.) there is no substance save God, nor any modifications save those (Prop. xv.) which are in God, and cannot without God either be or be conceived. Therefore the intellect, in function finite, or in function infinite, must comprehend the attributes of God and the modifications of God, and nothing else. Q.E.D.
Modern English
A true idea must agree with its object (E1A6), that is, as is self-evident, what is contained in the intellect as an object of thought must necessarily exist in nature. But in nature only one substance exists, namely God (E1P14C1), and no affections exist other than those that are in God and cannot, without God, either exist or be conceived (E1P15). Therefore the intellect, whether actually finite or actually infinite, must comprehend God's attributes and God's affections, and nothing else. Q.E.D.