Let us grant that, from this infinite number of rectangles, two only exist.

The ideas of these two not only exist, in so far as they are contained in the idea of the circle, but also as they involve the existence of those rectangles; wherefore they are distinguished from the remaining ideas of the remaining rectangles.
PROP.IX.

The idea of an individual thing actually existing is caused by God, not in so far as he is infinite, but in so far as he is considered as affected by another idea of a thing actually existing, of which he is the cause, in so far as he is affected by a third idea, and so on to infinity.
Proof .-- The idea of an individual thing actually existing is an individual mode of thinking, and is distinct from other modes (by the Corollary and note to Prop.viii.of this part); thus (by Prop.vi.of this part) it is caused by God, in so far only as he is a thinking thing.

But not (by Prop.xxviii.of Part i.) in so far as he is a thing thinking absolutely, only in so far as he is considered as affected by another mode of thinking; and he is the cause of this latter, as being affected by a third, and so on to infinity.

Now, the order and connection of ideas is (by Prop.vii.of this book) the same as the order and connection of causes.