Though there are many contemporary proofs of God (such as that of Bernard Lonergan), this contemporary version of St. Thomas Aquinas’ metaphysical proof of God, though difficult for newcomers, is brief and compelling.
It proves the existence of a unique unrestricted uncaused reality (existing through itself), which is the Creator of all else that exists.
Readers seeking more extensive explanations of the terms and the proof can make recourse to my book New Proofs for the Existence of God: Contributions of Contemporary Physics and Philosophy (Chapters 3&4).
A metaphysical proof always begins by showing the necessity of at least one uncaused reality in the whole of reality. Aristotle articulated this well about 2,400 years ago
– and its unfailing logic has remained quite similar ever since – with some refinements in logic and terminology.
The second premise of the proof shows that an uncaused reality (existing through itself) must be absolutely unrestricted.