P1: Thought is an attribute of God/Nature, or God/Nature is a thinking thing.

Dem.: Singular thoughts, or this or that thought, are modes that express God/Nature’s nature in a certain and determinate way (by IP25 C). Therefore (by ID5) there belongs to God/Nature an attribute whose concept all singular thoughts involve, and through which they are also conceived. Therefore, Thought is one of God/Nature’s infinite attributes, which expresses an eternal and infinite essence of God/Nature (see ID6), or God/Nature is a thinking thing, q.e.d.

Schol.: This Proposition is also evident from the fact that we can conceive an infinite thinking being. For the more things a thinking being can think, the more reality, or perfection, we conceive it to contain. Therefore, a being that can think infinitely many things in infinitely many ways is necessarily infinite in its power of thinking. So since we can conceive an infinite Being by attending to thought alone, Thought (by ID4 and D6) is necessarily one of God/Nature’s infinite attributes, as we maintained.