During the lecture, Lunine criticized the misguided attempts by modern scientists to prove or disprove the existence of God, which science is powerless to prove one way or the other. He highlighted the example of Stephen Hawking, who has said the following about God and creation:

You can’t get to a time before the Big Bang because there was no time before the Big Bang. We have finally found something that doesn’t have a cause, because there was no time for a cause to exist in. For me this means that there is no possibility of a creator, because there is no time for a creator to have existed in. [...] When people ask me if a God created the universe, I tell them that the question itself makes no sense. Time didn’t exist before the Big Bang, so there is no time for God to make the universe in (Hawking 2018, p. 37).

Lunine rebutted:

So this argument assumes the creator of the cosmos is a being who must exist in time. […] St. Thomas Aquinas, 800 years later, asserted that creation is not an event in time at some beginning, but something happening timelessly, everywhere and at each moment. [...] [Quoting Dominican priest and physicist Fr. Thomas Davenport] ‘Reality is held in existence by an omnipotent Creator, one who is not another part of nature, as Hawking’s argument implied, but rather is nature’s author and sustainer, totally and completely other to the created universe.’

Aquinas indeed described God as being “outside time altogether, without beginning or end,” (Feser 2009, p. 122) and that “[Creation] is an ongoing activity rather than a once-and-for-all-event. While the shoe might continue to exist even if the blacksmith dies, the music necessarily stops when the minstrel stops playing, and the world would necessarily go out of existence if God stopped creating it” (p. 88).

Lunine also pointed out an amusing irony: Hawking’s later theoretical work on the origin of the universe and time (like the no-boundary proposal or the holographic principle co-developed with Thomas Hertog) posits a timeless realm where creation is a continuous act. Hawking’s collaborator Hertog explained:

Holography paints a universe that is being continually created. It is as if there is a code, operating on countless entangled qubits, that brings about physical reality, and this is what we perceive as the flow of time. In this sense holography places the true origin of the universe in the distant future, because only the far future would reveal the hologram in its full glory (Hertog 2024, p. 244).

However, Lunine emphasized that his point was not to argue that “modern physics has validated Thomistic theology” but instead that science can “never be used to prove or disprove the existence of God,” as “one cannot get outside the universe with the tools of science because those tools are a part of the universe.”

If science cannot definitively prove or disprove the existence of God, how does a scientist come to believe in God? Lunine recommended as a resource Aquinas’ philosophical works such as Compendium Theologiae, “where Aquinas talks about how God’s essence is his existence; God is being itself.” Aquinas discusses these concepts of “essence” and “existence” in detail in one of his earlier works, De Ente et Essentia (On Being and Essence), where he demonstrates God’s existence based on the distinction between a thing’s essence (what it is) and its existence (that it is). He observes that in all created things, essence and existence are distinct; their existence is contingent and caused by another, not necessitated by their nature. Since these contingent beings cannot be the ultimate source of their own existence, and an infinite regress of contingent causes is insufficient to explain existence itself, there must be a first, uncaused being. This necessary being is unique because its essence is its existence; it does not receive existence but is existence itself (ipsum esse subsistens). Aquinas identifies this ultimate source of all beings, whose nature is pure existence, as God.

(By the way, for readers who are new to philosophy and find these explanations cryptic, I would recommend reading primers on Aquinas such as Edward Feser’s Aquinas or Peter Kreeft’s A Shorter Summa before diving into Aquinas’ full works.)

De Ente et Essentia lays the metaphysical foundation for his later works such as his magnum opus Summa Theologiae, which contains his famous “Five Ways” for demonstrating the existence of God. Aquinas goes on to derive the divine attributes consistent with the Christian God, including “perfection, infinity, immutability, and unity,” in works such as Summa Theologiae, Summa contra Gentiles, and De Potentia Dei (Feser 2010, p.97; Kreeft 1993, p. 66). In Summa Theologiae in particular, Aquinas systematically articulates Christian doctrine such as the Trinity and Incarnation by integrating arguments from reason with Scripture and Church tradition.

Lunine gave this lecture after Los Angeles’ first “Gold Mass for Catholics in the Sciences” celebrated at USC’s Our Savior Church, marking the 800th anniversary of the birth of St. Thomas Aquinas (Miller 2025). He concluded his talk by exhorting those in the audience pursuing a career in science to “do great science. And at the same time, embrace your faith. Open your heart to the God who loves you. You can do both. And by doing both, you will live a happier and more fulfilled life.”