June 19, 2019

Pruss and Rasmussen's Second Argument from Possible Causes

Traditional cosmological arguments typically include a premise about what things have causes or explanations. Modal cosmological arguments rely instead on a premise about what things could have causes or explanations. The aim of Pruss and Rasmussen's fifth chapter is to uncover the weakest/safest/most modest principle about possible causes that can be used to construct a valid modal cosmological argument. They arrive at the following (I retain their numbering):


  1. The W Principle: normally, for any property P, if (i) P can begin to be exemplified, (ii) P can have instances that have a cause; (iii) P is basic or a determinate of a basic property, and (iv) there is a determinate of P that can be caused to be exemplified, then there can be a cause of P's being exemplified.

  2. There is a property C such that C = being contingent.

  3. C can begin to be exemplified.

  4. C can have instances that have a cause.

  5. C is basic or a determinate of a basic property.

  6. There is a determinate of C that can be caused to be exemplified.

  7. Therefore, there can be a cause of the exemplification of C.

  8. If there can be a cause of the exemplification of C, then there is a necessary concrete thing.

  9. Therefore, there is a necessary concrete thing. (p. 100)


It is crucial to this argument that we are talking about a cause of the property's being exemplified at all, not a cause of a particular instance of the property. As a result, they can get a non-circularity condition without assuming that the kind of circular causation that happens in time travel stories is impossible (see the response to objection 5, pp. 107-108). This actually is a fairly intuitive account of the kind of explanatory gap that exists in the scenario where the "first" time machine is built by copying a time machine brought back from the future: in such a case, there is a cause of each instance of the property being a time machine, but there is no cause of that property's being exemplified at all, i.e., no cause of there being any time machines. The same is plausible with infinite chains: if, as Aristotle thought, there had always been humans and every human was born from human parents, then there would be a cause of each instance of the property humanity, but no cause of humanity's having any instances at all (unless some kind of atemporal cause of the whole series, but I think such a thing would be better described as a ground than a cause). Now, even if these kinds of cases are possible, it is nevertheless plausible to suppose (contrary to Aristotle) that it is also possible for there to be a cause of the exemplification of the property. If time machines are possible at all, then presumably it's possible for someone to invent one without copying a model. The human case is trickier if essentiality of origins applies to species. (Although Pruss and Rasmussen discussed objections from essentiality of origins in the previous chapter, they don't discuss that idea here.) If the property humanity is partly a causal/historical property, then perhaps it should be regarded as non-basic. But the case of being bipedal seems a lot like the time machine case: if it's possible at all, it should be possible for it to be caused.

As Pruss and Rasmussen note, the "normally" in The W Principle makes the inference to (14) defeasible. Otherwise, the argument is clearly valid. Further, (15) follows from S5 together with the non-circularity condition just described. The remaining premises, however, are open to question.

As usual, the authors motivate each premise, then consider a series of objections. It seems to me, however, that they do not consider the most important objection. The property C they have identified is a modal property, and this makes it unlike the examples that motivate The W Principle. Hence, it seems to me, an opponent could either say that The W Principle should not apply to modal properties (rejecting 8), or that modal properties are not basic properties or determinates of basic properties (rejecting 12). The authors offer no defense of (12) beyond the observation that existing contingently is "a determinate of the basic property of existence" (p. 102). This seems like cheating: arguably everything is a determinate of existence (possessing any property is a way of existing). In a footnote, the authors say that if you don't think existence is a property, you might think the property contingent existence is itself basic. Maybe. But actually this doesn't seem like a very plausible line for Pruss himself to take, since he endorses a powers theory of modality, so on his view an object exists contingently if, at some earlier time, there was a substance that had the power to initiate a causal chain whereby that object would not end up existing (or some such). That's an extrinsic property, and extrinsic properties are typically not thought to be basic. The same is going to be true if you construct modal properties out of possible worlds: contingency won't be a basic property of the object, since the predicate 'contingent' will apply in virtue of the object's non-existence in some other possible worlds, not in virtue of how the object is in the actual world.

In other words, my suggestion is that the opponent could either endorse a causal principle restricted to intrinsic categorical properties (or maybe intrinsic categorical properties plus primitive powers/dispositions, but not modal properties more broadly), or else hold that all basic properties are intrinsic categorical properties (plus primitive powers/dispositions). Perhaps there is some more complicated replacement for C that will still make the argument work if the opponent makes this move, but I don't know what it would be.

While the authors do not consider this among the objections in this chapter, it is closely related to the first weakness of the argument that they identify in their concluding assessment (p. 108): that the property C might be thought to be somehow special in a way that makes it not causable. The underlying issue here is that even if just any open formula specifies a property, it must not be the case that just any open formula specifies a basic property, else The W Principle wouldn't be any weaker than the principle employed in the previous chapter. So the issue of what properties are basic needs considerably more attention if we are to have any confidence that C is a basic property or a determinate of a basic property.

Posted by Kenny at June 19, 2019 3:57 PM
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