of the last Prop.) is constituted by certain modes of the attributes of God, namely (by II.Ax.

ii.), by the modes of thinking, of all which (by II.
Ax.

iii.) the idea is prior in nature, and, when the idea is given, the other modes (namely, those of which the idea is prior in nature) must be in the same individual (by the same Axiom).
Therefore an idea is the first element constituting the human mind.

But not the idea of a non--existent thing, for then (II.
viii.

Coroll.) the idea itself cannot be said to exist; it must therefore be the idea of something actually existing.