The Enigma of an Infinite Past
“Before the mountains were brought forth, or ever you had formed the earth and the world, from everlasting to everlasting you are God.”
— Psalm 90:2 (ESV)
One of the most common assumptions about the universe is that it may not have had a beginning at all. Perhaps time stretches endlessly into the past, moment after moment with no first day, no starting point. At first glance, this idea can sound reasonable, even sophisticated. After all, why must there be a beginning?
But when we slow down and think carefully about what an actual infinite past would require, a deep problem emerges, not merely scientific, but logical and metaphysical. This problem does not depend on advanced mathematics or speculative physics. It arises from something far more basic and unavoidable: the nature of time as a sequence of events.
To see this clearly, consider a simple illustration.
“An infinite temporal regress of events is impossible.”
— Aristotle, Physics, Book VIII
The Domino Illustration
Imagine a line of dominoes falling one after another. Each domino knocks over the next. Now imagine that this line stretches backward endlessly, an infinite number of dominoes into the past.
At the very end of the line stands one final domino. Let’s label that domino “Today.” Now ask a straightforward question:
If there were infinitely many dominoes before today, could the domino labeled “Today” ever fall?
The answer is no.
For “Today” to fall, the domino immediately before it must fall. For that domino to fall, the one before it must fall. And so on. If there is no first domino—no starting point—then the sequence can never be completed. The falling would never arrive at the final domino.
And yet, here we are. Today exists. The domino has fallen.
That simple fact tells us something profound: the past cannot be an actual infinite.
“Time is not something which exists apart from events; it is the order of succession.”
— J. M. E. McTaggart
Why This Is Not Just a Metaphor
Some will object, “But time isn’t really like dominoes.”
That is true. All analogies are limited. But the analogy works because time shares the relevant feature: it is successive. Moments occur one after another. Yesterday had to end for today to arrive. Last year had to pass before this year could begin.
This is not controversial. It is simply how time operates.
If the past were actually infinite, then reaching the present moment would require passing through an infinite sequence of earlier moments, one moment at a time. But an infinite sequence cannot be completed by successive steps. No matter how many moments pass, an infinite number would still remain.
Put simply: You can build forward forever from a beginning, but you cannot arrive at “now” if there was no beginning.
“If an actual infinite existed in reality, it would generate absurdities.”
— David Hilbert
Infinite Future vs. Infinite Past
This argument does not rule out an infinite future, and that distinction matters. An infinite future is open-ended. It is never completed. There is no final moment that must be reached.
An infinite past, however, would be a completed infinite, an infinite series of events that has already occurred. That is the problem. Completion is what makes an actual infinite metaphysically impossible in the real world.
This is why we can coherently affirm:
- An infinite future may be possible
- An actual infinite past is not
The Argument in Simple Form
P1. A series of events formed by successive addition cannot be actually infinite.
P2. The temporal past is a series of events formed by successive addition.
C. Therefore, the temporal past cannot be actually infinite.¹
But this conclusion immediately forces us to go deeper.
“To explain a thing by referring it to something else which equally needs explanation explains nothing.”
— G. K. Chesterton
Moving the Dominoes Back Does Not Solve the Problem
At this point, some respond by saying, “Perhaps this universe had a beginning—but maybe it came from something else: a singularity, a boundary, a multiverse, quantum tunneling, or some deeper cosmic structure.”
But this move does not solve the problem. It only moves the dominoes further back.
Return again to the illustration. Sometimes a falling domino splits the line into two, three, or many new lines. You now have multiple sequences instead of one. You might label these lines “multiverse,” “boundary,” or “cosmic tunnel.” But nothing essential has changed. No matter how many branches you add, all falling dominoes still require a first push.
Calling the earlier domino a “singularity” or a “quantum fluctuation” does not explain why it fell in the first place. Renaming the domino is not the same as explaining it. If the present universe exists because something earlier caused it, then that earlier reality also stands in need of an explanation.
Pushing the explanation backward is not explaining anything at all—it is postponing the question.
“Ex nihilo nihil fit.”
(From nothing, nothing comes.)
— Parmenides
The Unavoidable Conundrum
At some point, the chain of falling dominoes must stop being explained by earlier dominoes. Otherwise, the present moment would never arrive.
This leaves us with a stark and unavoidable choice.
Either:
- There was a first domino, something that initiated the chain without itself being caused by prior physical events,
or
- The dominoes began falling for no reason at all, caused by nothing, from nothing.
There is no third option.
And if “nothing” truly caused the first domino to fall, then explanation itself has been abandoned. The universe, and everything in it, would exist for no reason whatsoever.
That is not science.
That is not philosophy.
That is the end of rational inquiry.
“If the universe has a cause, that cause must be outside the universe.”
— Alexander Vilenkin
Why This Points Beyond the Universe
If the past is finite, then the universe began to exist. And whatever begins to exist requires an explanation.
Crucially, the cause of the universe cannot be part of the temporal sequence it brings into existence. It must therefore be:
- Timeless, because it created time
- Spaceless, because it created space
- Immaterial, because it created matter
- Powerful, because it brought the universe into existence
- Personal, because only an agent can initiate a temporal effect without a prior physical cause²
A timeless, impersonal cause would produce its effect eternally. But a personal agent can choose to act—bringing about a first moment without a prior moment.
This is what we mean by God.
To reject this conclusion not because the reasoning fails, but because one wishes to exclude God from the range of possible explanations, is to reason a priori; that is, to decide in advance what the answer cannot be, before examining the evidence or following the logic where it leads. It is to set a conclusion first and then evaluate arguments only insofar as they fit that pre-commitment. That is not a conclusion reached by reason, but a boundary imposed on it. If the premises are sound and the reasoning valid, then intellectual honesty requires following the argument where it leads—even if that destination is uncomfortable. To rule out God at the outset is not skepticism; it is a philosophical commitment made prior to the evidence.
“The first step in philosophy is to notice that not everything explains itself.”
— Etienne Gilson
The Final Word
The existence of “today” is not a trivial fact. It is a philosophical clue written into our experience of time.
The domino labeled “Today” has fallen.
And that means there was a first domino.
Appendix: Frequently Asked Questions and Objections
1. Doesn’t this confuse mathematics with reality?
No. Mathematics allows abstract infinities. This argument concerns whether an actual infinite can exist in the real world, where events occur one at a time.
2. You don’t have to count down from infinity to reach today.
Even if no one is counting, an infinite number of past moments would still have to elapse before today arrived. A sequence formed one step at a time cannot complete an infinite number of steps.
3. Maybe time doesn’t really “flow” this way.
If time is not successive, then causation, memory, change, and explanation collapse. All meaningful experience presupposes temporal succession.
4. What about multiverses or quantum origins?
These still describe physical realities with conditions and structures. Calling something “quantum” does not remove the need for an explanation of why it exists or why it produces effects.
5. Why must the cause be personal?
A timeless, impersonal cause would produce its effect eternally. Only a personal agent can initiate a temporal effect without prior physical conditions.
6. Isn’t this a God-of-the-gaps argument?
No. This is an inference to the best explanation based on the nature of time and causation, not an appeal to ignorance.
“There is no incoherence in the idea of an endless future; the incoherence lies in a completed infinite past.”
— William Lane Craig
Endnotes
- William Lane Craig, The Kalām Cosmological Argument (Eugene, OR: Wipf & Stock, 2000), 63–79.
- Paul Copan and William Lane Craig, Creation Out of Nothing (Grand Rapids: Baker Academic, 2004), 119–143.
- Alexander R. Pruss, The Principle of Sufficient Reason: A Reassessment (Cambridge: Cambridge University Press, 2006), 97–105.
- James E. Ross, “Infinity and Causation,” Philosophy of Science 35, no. 3 (1968): 259–270.
- Thomas Aquinas, Summa Theologiae, I.46.2.
Tom's Theology Blog 
Leave a comment