The implication of this argument, of course, is that God is the first and uncaused cause of the universe.
If Aquinas' argument is deductive, it is circular.
In a deductive argument the conclusion repeats what is already "stated" in the premises, explicitly or inexplicitly and, therefore, is assuming what needs to be verified.
If Aquinas' argument is inductive, his conclusion is only probable requiring verification.
Aquinas is guilty of committing the FALLACY OF COMPOSITION.
Arguments of composition fall into two categories:
The parts of a car are light, therefore the car is light.
The conclusion is false because the car is not light.
The parts of a car are heavy, therefore the car is heavy.
The conclusion is true because the car is heavy.
We shall not consider, here, the issue that the term, 'heavy,' is a value term.
It can be verified that a universe exists whatever may be its nature or limitations.
It cannot be verified that a non-corporeal god (i.e., first cause) or a Biblical god, defined to be non-matter/energy and unknowable, exists.
"Non-corporeal," by definition, means not matter: i.e., physically nothing.
It cannot be verified that "nothingness" can cause "somethingness."
It can be verified that something, i.e., matter/energy, (a verifiable composite term) can, with no evidence of instances to the contrary, cause something else.
It cannot be verified that the universe can cease to exist even if the universe is the so-called "pin-point" big bang.
It can be verified that the constituents of the universe can cease to exist and can come into existence, i.e., are contingent, and that the constituents of the universe contribute to both their existence and extension.
It cannot be verified that the universe (the existence of everything) reacts, i.e., relates to anything "outside" itself.
We are ignoring, here, the improper use of the term in sentences like, "There may be many universes."
The existence of the universe is a necessary condition for the contingency of its constituents.
The universe continues to exist despite its history of periodic losses of constituents.
To posit a non-corporeal, unknowable, unverifiable cause (whatever is the definition of "cause"--in this case "cause as the outmoded concept of force or power and the like") causing a corporeal entity into existence is unintelligible, sheer nonsense, and an abuse of language.
Furthermore, to posit an additional necessary non-corporeal "entity" is to fracture, or at least strain to the breaking point, the law of parsimony.
Occam had it right: Entities are not to be multiplied except as may be necessary!