For the self-evidence of the impossibility of infinite causal regress

Richard Hennessey follows a critique of the First Way given by Paul Edwards. Both note that St. Thomas says

But [a series of moved movers] cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover

They then draw a representative line of causes:


Edwards then objects:

This argument fails to do justice to the supporter of the infinite series of causes. Aquinas has failed to distinguish between the two statements:

(1) A did not exist, and
(2) A is not uncaused.

In other words, there’s no necessity for A to be a first cause in order to do its work – any second cause will work just fine. As Hennessey says more than once, he’s not denying that there is some A, only its “first causiness”.To put his argument another way, he is claiming that STA gives us two options: either A is the first cause, or there is no A. But this is an obvious false dichotomy, there could be an A that is a second cause.

Notice it makes no difference to the Hennessey’s argument whether one says that the causes in question are per se or per accidens, simultaneous or successive, etc. and so he’s right to object that those who divide different sorts of causes aren’t touching on his objection. He’s simply noting a false dichotomy in STA that is grounded in the saint’s failure to distinguish A being a first cause from A being at all.

Hennessey sets the bar pretty high for those who would disagree with him, since he says that St. Thomas’s premise is simply “not evident”. His post suggests a stronger disapproval, sc. that the premise is wrong – but at any rate I’ll argue against his stronger claim and say that the impossibility of infinite regress is evident.

There are two sorts of causes:

1.) Causes that are not effects.

2.) Causes that are effects.

Notice there is no difference between saying “a causal chain is infinite” and “all causes in the chain are 2’s”. The two statements express the same reality. The whole question of an infinite series, therefore, is whether all causes can be 2’s.

If all causes are 2’s, then causal power is always derived from another.  In concrete terms, this means that any time we find a cause, we will have to say “Ah, this thing has the feature of being a cause, but we know it got that feature from some other being”. The only reason we don’t see this is an absurd claim is because our notion of cause is cloudy and abstract. Consider if we actually gave this sort of explanation for a more concrete feature of things, say, the stability of the earth. The earth clearly has a stability that is there to be explained: we can build houses on it; we pour foundations into it; we leave landmarks and permanent statues in it, etc. Now everyone agrees that it is impossible to explain this stability by saying that the earth rests on a giant tortoise. Why so? Can’t a giant tortoise have the requisite stability to explain why the earth doesn’t move? Yes, but any stability tortoises have would have to come from another – it’s not as if they have stability in the way that triangles have three sides or men are risible. But there would be nothing wrong with the “tortoise hypothesis of stability” if infinite causal regresses could really explain the features of things.

Infinite causal regresses, in other words, are manifestly and evidently ridiculous things – it is only because causality is a fainter, less concrete notion to us that we don’t see this immediately, and even without having to think about it. In any concrete instance of explaining things, we can see right away that infinite causal regresses can neither explain or be the source of the being of anything. All of them are tortoises invoked to explain the stability of the earth, or little men behind our eyeballs invoked to explain consciousness.

The upshot is that explaining anything, from heat to stability to consciousness, requires the reduction to some first cause. We know this naturally and don’t  suggest otherwise unless we are confused about what we are  saying. In this sense, the finite causal regress of any feature of things – causes included – is known spontaneously by everybody and is therefore per se nota, or self- evident in the strongest sense of the term.


  1. August 26, 2010 at 7:55 pm

    While I’m inclined to agree with you that the impossibility of an infinite causal regress is self-evident, I’m usually drawn more to arguments that seek to establish this fact. Not that this is necessary, but it’s just a matter of interest, as I’m sure it is for you, as well. What do you make of the following inductive argument?:

    1. For any non-temporal causal regress, that regress is either finite or infinite. (Definition)
    2. The causal regress of X is an attribute of X. (Premise)
    3. If every observable attribute of X is finite, then the causal regress of X is most likely finite. (Premise)
    4. Every observable attribute of X is finite. (Premise)
    5. Therefore, the causal regress of X is most likely finite. (From 1 – 4)

    In your estimation, would this constitute a philosophically cogent inductive argument against an infinite regress of non-temporal causes?

    • August 27, 2010 at 3:19 pm

      I wonder about #4. To explain: “infinite” is the negation of the finite, that is, the negation of a beginning and an end. In a finite causal series like


      A has a beginning in itself (that is, it is the beginning), C has the end in itself, but B of itself has neither the beginning nor the end. Or itself it lacks termination and so is infinite. This infinity of B is exactly the sort of infinity that makes the infinite regress. An infinite regress is simply the claim that all causes are B’s, that is, that they lack termination or finite existence in themselves. They are infinite in the empty, vain sort of infinity that the Greeks abhorred, and which they could see more clearly than we can. In this sense of infinite only God is entirely and absolutely finite, for only he of his very nature is both his origin and final end.

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