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Introduction to Pruss and Rasmussen, Necessary Existence

One of my projects this summer is a review of Alexander Pruss and Joshua Rasmussen's Necessary Existence for American Catholic Philosophical Quarterly. I read the book for the first time a few months ago, but I'm now working through it more carefully in preparation for writing the review. I've often found it helpful in the past to write a blog post about each chapter of a book and then condense them into a review, and I'll be doing that here over the next couple of weeks.

The project of the book is to investigate arguments for the claim that there exists a necessary being. In the introduction, a 'necessary being' is defined as something that exists necessarily and is "capable of causation" (p. 2). Hence this is not a book about mathematical platonism or anything of that nature. The question is whether there might be a necessarily existing being that can enter into causal relations.

Although both authors of the book are well-known for their work in philosophy of religion, and this book examines a metaphysical thesis that is highly relevant to philosophy of religion, the authors are very careful to say that this is not a philosophy of religion book, since the nature of the necessary being is not investigated and the question of whether a necessary being would deserve the name 'God' (or have any relevance to religion) is very much an open question (sect. 1.2). Nevertheless, the authors do give a brief argument for the claim that if God exists and at least one necessary being exists then God is a necessary being (pp. 5-6).

I do want to note a reservation I have about this argument. The argument goes basically like this: if God exists, then God must be the source of all there is apart from God. So, if God exists and a necessary being exists, then either God is identical with the necessary being or God is the source of the necessary being. The source of a necessary being must itself be a necessary being.

My reservation is this: I've argued that the manner in which God is the source of all things is best understood in a non-causal way, but Pruss and Rasmussen define a necessary being as something that exists necessarily and can enter into causal relations. Now, I do think that God is a necessary being in this sense because I think that God can enter into causal relations (see footnote 10 of the just-linked paper). But if I'm right that God can be the source of things in a non-causal way, then there is a missing step in the argument. Someone who agrees with me that God's ultimate sourcehood should be understood non-causally might disagree with my view that it is possible that God nevertheless enter into some causal relations. If God can't interact causally, but is nevertheless the ground of all being, then God does not count as a necessary being as Pruss and Rasmussen define that phrase. Note here that, while the authors are very logically careful and seem always to bear their official definition of 'necessary being' in mind, there is potential for confusion on the part of the reader since existing necessarily is not sufficient for being a necessary being in the stipulated sense. If creation is non-causal, then someone could hold that God exists necessarily and necessarily is the source of all that is and nevertheless hold that God is not a necessary being, in Pruss and Rasmussen's sense.

One way to try to plug this hole would be to emphasize how broadly Pruss and Rasmussen use the phrase "capable of causation." They write: "We intend the term 'cause' in a minimal sense to designate anything that acts as an antecedent condition (or entity) that is at least partially causally responsible for some event" (p. 2). In this "minimal" sense, perhaps it could be said that something that grounds the cause of an event also counts as an antecedent entity partially causally responsible for the event. An interesting consequence of this move would be that a certain kind of (broadly) Pythagorean view on which mathematical entities partly ground physical entities would make (at least some) mathematical objects turn out to be necessary beings (in Pruss and Rasmussen's sense) after all. But perhaps this would not be such an unwelcome consequence: if mathematical objects (at least partly) ground entities that enter into causal relations then there's a perfectly good sense in which mathematical entities are not causally inert. Certainly this kind of view does not deflate the claim that there's a necessary being: commitment to mathematical objects of this sort is a piece of heavy-duty metaphysics.

None of this undermines the broader project of the book, to which we now return.

The goal, as I said, is to examine arguments for the existence of a necessary being. The Introduction gives only a hint of how this will proceed, but the hint is a good one. Section 1.3 discusses an online survey undertaken a few years ago to try to determine how many people (including how many philosophers) who did not believe in a necessary being nevertheless endorsed some premises that logically entailed that thesis. The authors report that the numbers were quite high, including among (self-identified) philosophy professors. But note that the survey was not asking about the premises of some one argument. It was much more like a "Choose Your Own Adventure" book. (I believe I was in fact one of the survey respondents, but I don't have detailed memory of the survey.) And it is this that gives the flavor of the present book: the reader is constantly faced with philosophical choices, but (almost) all routes end up the same place, namely, at the existence of a necessary being.

This book is an example of analytic philosophy at its best. It is extremely logically careful, drawing only the conclusions warranted by its explicitly stated premises. It is technical where technicality is needed (including in some very interesting arguments about the bearing of Godel's incompleteness theorems on the nature and logic of possibility and necessity) but dispenses with technicality where it can be dispensed with. Most importantly, it makes a convincing case for a surprising thesis. The thesis is not precisely that a necessary being exists. Rather, I would express the thesis like this: you might have thought that the claim that there is a necessary being was a heavy duty metaphysical commitment, carrying with it all sorts of philosophical baggage, but in fact the reverse is more nearly correct. It turns out that a very wide range of philosophical views entail the existence of at least one necessary being, so that only certain very precisely constructed philosophical systems are consistent with the denial of necessary beings.

Such, at least, is how I remember my very positive response to the book when I first read it months ago. Stay tuned over the next few weeks to see how it holds up under closer scrutiny.