blog.kennypearce.net

Pruss and Rasmussen's Necessary Existence: Conclusion and Table of Posts

Pruss and Rasmussen conclude with an appendix providing "a slew of arguments" for the claim that there is a necessary being. These arguments are, for the most part, presented without defense or other comment, and it is clear that the authors do not actually endorse the premises of all of them. However, they contribute to the book's broader purpose of showing that the existence of a necessary being is difficult to avoid, and that determination to avoid it commits one to some substantive philosophical views.

Every one of Pruss and Rasmussen's arguments leaves open certain paths for the opponent to avoid the conclusion. This is true of philosophical arguments generally. Yet every argument has premises that will seem at least somewhat attractive to many opponents. In this way, the book is certainly successful in what it sets out to do, and I retain my initial assessment that this is analytic philosophy at its best.

Opponents looking to make particular moves to avoid each argument individually will find themselves burdened by quite a large array of philosophical commitments in order to avoid the conclusion that there is a necessary being. Yet the arguments are sufficiently diverse that it is difficult to think of general strategies for defusing all of them, rather than proceeding case by case. I can see two such general strategies: the opponent can target either Pruss and Rasmussen's modal logic, or their use of causation.

Almost every argument in the book makes use at some point on the principle: ◊□p ⊃ p. This principle is equivalent to the Brouwer axiom.* So the rejection of the Brouwer axiom would undermine nearly all of the arguments. For this reason, it is to their credit that in chapter two Pruss and Rasmussen undertake to defend S5 (which is equivalent to S4 + Brouwer), even though most analytic metaphysicians and philosophers of religion today simply assume it. I would tend to think that adopting a non-standard modal logic, which is more complex than the standard one, would be inherently costly for a theory, but even if someone didn't think that, the chapter shows the costs involved in trying to reject S5.

Pruss and Rasmussen's position with respect to causation is less strong. Here they make assumptions that I think are probably more controversial than S5. However, not all of their arguments make precisely the same assumptions. Someone who was willing to take an eliminativist line on causation could undermine all the arguments in one fell swoop, but that's a really hard line, and so would certainly count as undertaking a serious philosophical commitment in order to avoid the arguments. How the arguments might fare under different forms of reductivism, deflationism, or anti-realism is less clear to me, and because the arguments don't make precisely the same assumptions about causation showing that a certain theory simultaneously blocks all of them would be a quite significant task. It seems to me, then, that Pruss and Rasmussen have done quite a lot to show that the existence of a necessary being is not an easily jettisoned piece of unnecessary philosophical baggage, and, indeed, that it's denial carries quite significant baggage. In other words, this book seems to me to be a success and I warmly recommend it.

Table of Posts

1. Introduction
2. Modal Logic
3. The Argument from Contingency
4. First Argument from Possible Causes
5. Second Argument from Possible Causes
6. Modal Uniformity
7. Necessary Abstracta
8. The Gödelian Ontological Argument
9. Arguments Against a Necessary Being

Note