Def 1: A contingent being is a being such that if it exists, could have not-existed or could cease to exist.
Def 2: A necessary being (or non-contingent being) is a being such that if it exists, cannot not-exist (and therefore could not not-have-existed and cannot cease to exist).
Note: I use ground-reason essentially to do the work of the German Grund, a word which neither the English “ground” nor “reason” sufficiently captures in meaning, since it unites the sides of being and knowing, the ontological and the epistemological, in one.
1. A contingent being C exists.
2. This contingent being C has a ground-reason for its existence.
3. If C were the ground-reason for C’s existence, C would not be a contingent being, but a necessary one, since C, as self-grounding, could not not-exist—contrary to 1.
4. Therefore, the ground-reason for C’s existence must be something other than C.
5. This ground-reason for C’s existence other than C must either be another contingent being or set of contingent beings alone or it must be or include a non-contingent (necessary) being N.
6. Contingent beings alone cannot provide a completely adequate ground-reason for the existence of any contingent being (neither ontologically as ground nor rationally as reason), so the ground-reason for C’s existence is not any contingent being or set of contingent beings alone.
7. Therefore, the ground-reason for the existence of contingent being C must be or include a non-contingent (necessary) being N.
8. Therefore, a necessary being N exists, because without such a necessary being N, C could not exist, contrary to 1.
9. The universe and every part of the universe is contingent (as is “the multiverse” and every part of it, if this concept is supposed to subsume “universe”).
10. Therefore, a necessary being N which is something other than the universe or one of its parts (or “the multiverse”), must be the ground-reason for its existence.
11. Therefore there exists a necessary being N which is the ground-reason for all contingent beings, including the universe or cosmos or multiverse, as well as all their parts, whatever they may be.
12. Et hoc omnes intelligunt Deum.
Premise 1: This premise is empirical but evident. As long as anything at all exists which could have not existed or could cease to exist, it is a contingent being. It is obvious that physical beings are contingent.
Premise 2: This is simply a statement of the Satz vom Grund or Principle of Ground (usually expressed in English as the Principle of Sufficient Reason), although perhaps the Principle of Ground-Reason would be better as I use it. This principle can be expressed negatively as “nothing happens or comes about FOR NO REASON.” It is a core principle about reality, that things cannot happen for no reason at all, just as it is about reality that a thing can’t both be and not be the same at the same time and in the same respect—and because Being is like this, thinking (which follows being) has the Principle of Ground and the Principle of Noncontradiction as basic first principles.
Premise 3: Evident. If C were its own ground-reason it could sustain itself in being and never cease to be, and would thus be a necessary being; but C is already posited in 1 as contingent, so it can’t be the ground-reason of itself.
Premise 4: Also evident. Since C is not its own ground-reason, the ground-reason of C must be something other than C.
Premise 5: By the Principle of the Excluded Middle, this something other than C is either fully contingent or contains a necessary being.
Premise 6: This is the premise that would take the most argumentative work to establish and to get clear about. Since in contingent beings, existence is a property that is “passed on” from another being, if a contingent being got its existence from another contingent being, that being would have to be either contingent or necessary. In this scenario in Premise 6, no necessary beings are in play. So one would have to hold either that there is an infinite regress of contingent beings each passing on their being to another being and receiving it from the one before—most philosophers think the idea of an actual infinite is absurd (conceptual or abstract infinites are not). Or the passing on of existence would have to be circular, where A causes B to be and B causes C to be and C causes A to be. This becomes more clear, perhaps, when we look at it from the side of explanation, as the reason for C: I want to explain how C got here, so I say C₋₁ explains C, but C₋₁ is explained by C₋₂ and it by C₋₃ and it by C₋₄ … infinitely C₋∞. But this “explanation” never actual explains anything. In simply passes the buck infinitely backwards. It is as if I wanted to know the origin of a magic book that contains the secrets of the cosmos, and someone tells me he got it from his father, who got it from his father, who got it from his father … who … etc. No matter how long you make this chain of fathers passing down books to sons, you never answer “Yes, but where did the book originate?” We need something it terminate the infinite regress, where the “buck” of explanation can no longer be passed. Similarly, it would be famous for the possessor of the book, Dave, to explain he got it from Mary, who got it from Josh, who, is it happens, got it from Dave. If I said to Dave, “Yes, I know Mary gave it to you, but where did it come from?” it would not do for Dave to say “I always get it from Mary, who always gets it from Josh, and I always give it to Josh. This circuit is itself the origin of the book.”
Premise 7: If it is correct, then, that the ground-reason for a contingent being cannot be nothing but other contingent beings, whether in the mode of an infinite regress (which is a non-explanation) or a circular explanation (which is a non-explanation), then it must be the case that there is a necessary being which terminates the regress.
Premise 8: Since C requires there be a necessary being N in order for C to be, and C is (premise 1) then there is an N.
Premise 9: The argument from 1-8 applies to every being without the universe, all of which are contingent, as well as the whole ensemble of contingent beings called the universe. A whole made entirely of contingent beings cannot itself be necessary, since it is susceptible to change—which a necessary being cannot be. Someone might say that an inference from the things that make up the universe to the whole universe might be a fallacy of composition, but this cannot be the case, since the universe is an aggregate that contains contingent parts and therefore changes.
Premise 10: The same argument 1-8 reapplied to the universe as contingent. There must be something other than the universe, a necessary being N, which is the ground-reason for the universe.
Premise 11: So there is such a necessary being N which is other than the universe and is its ground-reason.
Premise 12: Bit of a joke. This is a variant of how St. Thomas Aquinas ends each of his Quinque Viae or “Five Ways” of proving the existence of God: “And this everyone understand to be God.”
As a piece of natural theology, the argument from contingency will indeed not get one straight to the Christian God—but then, it isn’t meant to. It will get is to “there is a being other than the universe such that it is the ground-reason for the universe’s existence and is in itself a necessary being, such that it has the ground-reason for its own existence in itself.
From there we can go on to flesh out what other things this entails about such a being: if we work through it will find out it is timeless, spaceless, unchanging, and perfect.
In other words, it is very certainly AT LEAST what Jews, Christians, and Muslims call “God, what Hindus call Brahman, what the Chinese call “The Tao,” what Plato knew as “The Idea of the Good,” Etc.
The argument from contingency isn’t enough to settle the theological question of what God is like, but it is enough to show that atheism is false and agnosticism unwarranted.