Pruss's Cannonball and the Leibnizian Cosmological Argument

ROUGH DRAFT

A standard criticism of the Leibnizian cosmological argument exploits the point that there are cases in which a whole is explained in virtue of its parts. Examples:

Hume: 

...in such a chain or series of items, each part is caused by the part that preceded it, and causes the one that follows. So where is the difficulty? But the whole needs a cause! you say. I answer that the uniting of these parts into a whole, like the uniting of several distinct counties into one kingdom, or several distinct members into one organic body, is performed merely by an arbitrary act of the mind and has no influence on the nature of things. If I showed you the particular causes of each individual in a collection of twenty particles of matter, I would think it very unreasonable if you then asked me what was the cause of the whole twenty. The cause of the whole is sufficiently explained by explaining the cause of the parts.

-Dialogues Concerning Natural Religion, Part IX

Paul Edwards:

The demand to find the cause of the series as a whole rests on the erroneous assumption that the series is something over and above the members of which it is composed. It is tempting to suppose this, at least by implication, because the word "series" is a noun like "dog" or "man." Like the expression "this dog" or "this man" the phrase "this series" is easily taken to designate an individual object. But reflection shows this to be an error. If we have explained the individual members there is nothing additional left to be explained. Supposing I see a group of five Eskimos standing on the corner of Sixth Avenue and 50th Street and I wish to explain why the group came to New York. Investigation reveals the following stories: 

- Eskimo No. 1 did not enjoy the extreme cold in the polar region and decided to    move to a warmer climate. 

- No. 2 is the husband of Eskimo No. 1. He loves her dearly and did not wish to live without her. 

- No. 3 is the son of Eskimos 1 and 2. He is too small and too weak to oppose his parents. 

- No. 4 saw an advertisement in the New York Times for an Eskimo to appear on television. 

- No. 5 is a private detective engaged by the Pinkerton Agency to keep an eye on Eskimo No. 4. 

Let us assume that we have now explained in the case of each of the five Eskimos why he or she is in New York. Somebody then asks: "All right, but what about the group as a whole; why is it in New York?" This would plainly be an absurd question. There is no group over and above the five members, and if we have explained why each of the five members is in New York we have ipso facto explained why the group is there. It is just as absurd to ask for the cause of the series as a whole as distinct from asking for the causes of individual members.

          -"The Cosmological Argument" (1959)

Alexander Pruss offers a reply (section 4.1.1.4) to this sort of objection. His strategy is to use the examples from Hume and Edwards to generate a variations on a general explanatory principle (the so-called 'Hume-Edwards Principle'), and then to offer counterexamples to them. Thus, after some chisholming, Pruss considers the following explanatory principle to be the most plausible:

(HECP) For any proposition p such that one has explained every conjunct of a proposition, one might have thereby explained the whole.

(where "might" is construed as epistemic possibility)

In reply, Pruss offers the following as a counterexample to HECP:

At noon, a cannonball is not in motion, and then it starts to fly.  The cannonball flies a long way, landing at 12:01 pm.  Thus, the cannonball is in flight between 12:00 noon and 12:01 pm, in both cases non-inclusive. 

Let p_t be a proposition reporting the state of the cannonball (linear and angular moment, orientation, position, etc.) at time t.  Let p be a conjunction of p_t over the range 12:00 < t < 12:01.  I now claim that p has not been explained unless we say what caused the whole flight of the cannonball, e.g., by citing a cannon being fired.  This seems clear.  If Hume is right and it is possible for causeless things to happen, then it could be that there is no cause of the whole flight.  But that is just a case where p has not been explained.  To claim that there was no cause of the flight of the cannonball but we have explained the flight anyway would be sophistry. 

But if the HECP is true, then there might be an explanation of p without reference to any cause of the flight of the cannonball.  For take any conjunct p_t of p.  Since 12:00 < t, we can choose a time t* such that 12:00 < t* < t.  Then, p_t is explained by p_t* together with the laws of nature and the relevant environmental conditions, not including any cause of the flight itself.  By the HECP wemight have explained all of p by giving these explanations.  Hence, by the HECP we might have explained the flight of a cannonball without giving a cause to it.  But that is absurd.

What to make of this reply? One might worry that it's uncharitable to assume that Hume and Edwards are assuming a general explanatory principle in their examples and relying on it for the epistemic force of their point. Relatedly, one might worry that making such an attribution and then offering counterexamples to it is a red herring, as such general principles aren't required for the success of their criticisms. For their success only requires that (i) they represent singular epistemically possible cases where an explanation of each part of a thing or state of affairs thereby provides an explanation of the whole, and that (ii) such cases are relevantly similar to those the cosmological argument must exclude; showing that there are counterexamples to the general principles that Pruss attributes to Hume and Edwards is consistent with the claim that the particular examples of Hume and Edwards (or analogues thereof) are genuine, relevant cases of wholes explained in terms of facts about their parts. 

But let's waive these worries, as Pruss seems to recognize as much:

Thus not only is the HECP false in general, but it is false precisely in the kind of cases to which Hume, Edwards and Campbell want to apply it: it is false in the case of an infinite regress of explanations, each in terms of the next.

Is Pruss's reply, thus sharpened, successful? 

No, it isn't. For there are at least two different sorts of infinite regresses to consider here: (i) those involving a clear case of a prior originating cause of the series, and (ii) those that don't. Now Pruss's cannonball example seems telling against the sufficiency of HECP for adequate explanations of facts in a type-(i) series.  But the problem is that the relevant sort of infinite regress here is that of type-(ii). For what cries out for explanation in Pruss's cannonball case is the cannonball's transition from a state of rest to a state of motion. The relevant sort of parallel case here would thus be one involving an explanation for a transition from a state of there being no universe (or at least no matter-energy) to a state of there being a universe. But most naturalists take the universe's history (or at least matter-energy's history) to be beginningless, and therefore lacking any such transition. Unlike Pruss's cannonball scenario, therefore, the former scenario lacks a comparable transition that cries out for explanation. It therefore looks as though Pruss has failed to deflect the Hume-Edwards criticism at issue.