P45: Each idea of each body, or of each singular thing which actually exists, necessarily involves an eternal and infinite essence of God/Nature.

Dem.: The idea of a singular thing which actually exists necessarily involves both the essence of the thing and its existence (by P8 C). But singular things (by IP15) cannot be conceived without God/Nature—on the contrary, because (by P6) they have God/Nature for a cause insofar as he is considered under the attribute of which the things are modes, their ideas must involve the concept of their attribute (by IA4), i.e. (by ID6), must involve an eternal and infinite essence of God/Nature, q.e.d.

Schol.: By existence here I do not understand duration, i.e., existence insofar as it is conceived abstractly, and as a certain species of quantity. For I am speaking of the very nature of existence, which is attributed to singular things because infinitely many things follow from the eternal necessity of God/Nature’s nature in infinitely many modes (see IP16). I am speaking, I say, of the very existence of singular things insofar as they are in God/Nature. For even if each one is determined by another singular thing to exist in a certain way, still the force by which each one perseveres in existing follows from the eternal necessity of God/Nature’s nature. Concerning this, see IP24 C.