An Existential Proof Redux
- I exist. [Introspectively true]
2. What I am is a thinking thing — I experience myself as thinking, and so as existing. [Descartes’ res cogitans argument]
3. But what I am — a thinking subject — is distinct from the fact that I am.
4. So, the fact that I exist is not explained by the kind of being that I am, which is to say that it is not of my essence to exist.
5. Because my essence is distinct from my existence — and therefore the fact that I exist is not explained by the kind of being that I am — there must be an efficient cause to account for my being as the kind of being that I am — that is, there must be an efficient cause capable of conjoining essence and existence.
6. This efficient cause must be responsible for the conjoining of my essence and existence, here and now, and at every point at which I exist, since at no point at which I exist does my essence entail my existence. We are thus concerned with an efficient cause that is logically prior, and not temporally prior.
7. This cause must be a) itself a composite of essence and existence, or b) it must be such that in it essence and existence are not distinct, but identical. There are no other possibilities.
8. Now, anything in which essence and existence are distinct will itself require an efficient cause, since its essence will not account for its existence any more than the essence of a unicorn accounts for its real existence.
9. But in any non-temporal series of causes in which one essence/existence composite is conjoined by a further, logically prior essence/existence composite, one cannot proceed to infinity. For if every member in the series exists only in a derivative way — insofar as its essence and existence are at all times conjoined by some extrinsic cause — then, unless there is a cause of the causality operating throughout the series — a first cause  — then the series of composite existents would simply fail to exist.
10. So, my existence here and now must be efficiently caused by something in which essence and existence are not distinct, but identical.
11. Something in which essence and existence are identical is what, among other things, we traditionally mean by “God”. 
12. So, God exists.
: We mean “first cause” in the sense of being the ultimate or most fundamental cause of every essence/existence composite.
: We may go further and say that the ultimate cause of my ongoing existence must be necessary, since it is of its very essence to be; it must also be immaterial, since every material being is a composite of essence and existence. Other divine attributes such as omnipotence, eternity, simplicity, etc. follow from the conclusion of premise 10.