Monday, 31 August 2009

Swinburne: The Intrinsic Probability of Theism

In Chapter 5, The Intrinsic Probability of Theism, Swinburne looks again at the definition of the theistic God and adds more detail to it, and then makes his assessment of its prior probability in terms of how simple he finds the conception of God to be.

Whether you agree or not with Swinburne’s idea that a simple concept has a higher prior probability than a complex one (I don’t, because the concept of prior probability is meaningless in this context), it is worth examining this concept of simplicity. All the evidence of the universe available to us is that complex things develop slowly through natural processes from simpler ones. This applies not only to life through evolution, but apparently also to the relatively complex present structure of the universe from simpler beginnings. So even though I find Swinburne’s talk of prior probability entirely misguided, there is still the point that the start of the universe apparently needs to be something simple.

Let’s take a look at what Swinburne thinks of this, starting with Swinburne’s understanding of God

There exists now, and always has existed and will exist, God, a spirit, that is, a non-embodied person who is omnipresent. … In essence, to say that God is disembodied is to deny that there is any volume of matter such that by his basic actions he can control only it and such that he knows of goings-on elsewhere only by their effects on it. By contrast, to say that God is an omnipresent spirit is to say that he knows about goings-on everywhere without being dependent for that knowledge on anything, and can control by basic actions all states of affairs everywhere (in this or any other universe) without being dependent for that power on anything. God is creator of all things in that for all logically contingent things that exist (apart from himself) he himself brings about, or makes or permits other beings to bring about, their existence. He is, that is, the source of the being and power of all other substances.

Clear enough. According to his hypothesis, God created everything, is everywhere, and can do anything not logically contradictory. He then goes on to justify this in terms of simplicity, in order to claim that the hypothesis that there is such a being has a high prior probability.

To start with, theism postulates a God who is just one person, not many. To postulate one substance is to make a very simple postulation.

Quite why one is simpler than zero is not stated. But never mind. Let us continue.

He is infinitely powerful, omnipotent. This is a simpler hypothesis than the hypothesis that there is a God who has such-and-such limited power (for example, the power to re-arrange matter but not to create it). It is simpler in just the same way that the hypothesis that some particle has zero mass, or infinite velocity is simpler than the hypothesis that it has a mass of 0.34127 of some unit, or a velocity of 301,000 km/sec. I finite limitation calls out for explanation of why there is just that particular limit, in a way that limitlessness does not.

I must say that Swinburne is being very selective here. He claims that there must be a limit to human understanding of the universe, and that the existence of this limit doesn’t need explanation, but that there is no limit to the powers of God, and this lack of a limit also requires no explanation. In fact, anything that he chooses to posit appears to require, by definition, no explanation.

As I noted in chapter 3, scientists have always preferred hypotheses of infinite velocity to hypotheses of very large finite velocity, when both were equally compatible with the data. There is a neatness about zero and infinity that particular finite numbers lack.

This is simply ignorant. Swinburne is trying to claim scientific justification for his hypotheses without having taken the trouble to find out how scientists actually think. Scientists haven’t always preferred infinities and zeros and they don’t today. Since Swinburne is keen on talking about Newton and gravity, let us note that Newton himself was extremely bothered by the fact that the action of gravity by his equations appeared to operate at infinite speed – and yet the equations didn’t work for a finite speed for gravity. Newton wrote the following to a colleague in 1692.

“That one body may act upon another at a distance through a vacuum without the mediation of anything else, by and through which their action and force may be conveyed from one another, is to me so great an absurdity that, I believe, no man who has in philosophic matters a competent faculty of thinking could ever fall into it.”

Newton was careful to say that he didn’t know why gravity works and what causes it, merely that it does work according to the equations. In the second edition of Principia he wrote.

“I have not yet been able to discover the cause of these properties of gravity from phenomena and I feign no hypotheses... It is enough that gravity does really exist and acts according to the laws I have explained, and that it abundantly serves to account for all the motions of celestial bodies.”

By the way, this also refutes the idea suggested in a previous chapter that scientists were satisfied at the time that Newton’s laws represented a terminus in scientific understanding.

Anyway, on with Swinburne’s simplicity of theism.

Yet a person with zero powers would not be a person at all. So in postulating a person with infinite power, the theist is postulating a person with the simplest kind of power possible.

By accident, Swinburne lets slip a fundamental weakness of his case, even stated in its own terms. A lack of a person, and therefore no associated powers, is simpler – it is zero in both cases, whereas a single person with infinite powers is a single person, and therefore more complex. But onward…

God’s beliefs have a similar infinite quality. Human persons have some few finite beliefs, some true, some fasle, some justified, some not. In so far as they are true and justified (or at any rate justified in a certain way), beliefs amount to knowledge. It would seem most consonant with his omnipotence that an omnipotent being have beliefs that amount to knowledge. For, without true beliefs about the consequences of your actions, you may fail to realize your intentions.

This isn’t making any kind of argument about simplicity. This is merely taking a premise (that God is omnipotent) and following a line of argument that leads to a conclusion that God is also omniscient. The value of the conclusion is only as good as its premise, and so this line of reasoning doesn’t seem to add anything to his claims of prior probability at all.

For a person to act, he has to have intentions. A person could be omnipotent in the sense that whatever (logically possible) action he formed the intention to do, he would succeed in doing, and also omniscient so that he knew what were all the (logically possible) actions available to an omnipotent being in his situation, and yet be predetermined to form certain intentions. His intentions might be determined by causal factors outside his control, or at any rate, as are those of humans, greatly influenced by them. But, if a person is predetermined (or has an inbuilt probabilistic tendency) to act in certain specific ways, this means that a tendency to act in certain ways is built into him. But a person with an inbuilt detailed specification of how to act is a much more complex person than one whose actions are determined only by his uncaused choice at the moment of choice. Such a being I call a perfectly free being. Theism in postulating that God is perfectly free makes the simplest supposition about his choice of intentions.

This tells us nothing about whether such a being is possible. It seems to me that the greater the capabilities, the greater the complexity needed in order to achieve them, and if there is perfect freedom in terms of intentions, then I suggest that involves quite a lot of capability.

A substance who is essentially omnipotent, omniscient, and perfectly free is necessarily a terminus of complete explanation. For if some state of affairs E is explained as brought about by God in virtue of his powers and beliefs and intentions, to bring about E, how can the action be further explained?

Well, it would help if there were an explanation of how God came to be in the first place. Swinburne argues as follows

God’s being omnipotent, omniscient, and perfectly free is involved in his existing, given that, as we have supposed, these qualities belong to the divine essence. But his existing cannot be due to any contemporaneous factor that makes him exist or allows him to exist. For, if his existence depended on some factor apart from himself, that factor could not depend for its existence on himself (for one cannot have causation in a circle). But if this factor did not depend on God, then God would not have been able to make it exist or not exist, and so would not be omnipotent.

It seems to me that Swinburne has rather painted himself into a corner here. There is no means of explaining the existence of an omnipotent God, since any factor causing God to come into being is by definition not under God’s control, and this would render God not omnipotent. But if he isn’t omnipotent but has circumscribed powers, then the limit of those powers is something which in turn needs to be explained.

Therefore, we simply have to accept the prior probability of a God whose existence (in the form defined by Swinburne) is fundamentally inexplicable without engaging in logical contradictions.

But despite all this, Swinburne grandly concludes.

The intrinsic probability of theism is, relative to other hypotheses about what there is, very high, because of the great simplicity of the hypothesis of theism.

I notice he manages to reach the end of the chapter and conclude that theism is intrinsically more probable than any other hypothesis without considering in detail or even naming any other hypotheses. Moreover he has incorrectly stated the necessary comparison. The correct comparison is the hypothesis of theism against the sum of all hypotheses which do not posit the existence of the theistic God.


  1. As expected, Swinburne's "simplicity" and theology is laughable. But I'd like to highlight a few side points -

    As far as Swinburne is concerned, there is no complexity in having personal properties like desires, will, beliefs, power, and so on. All these come completely free. This is of course absurd, belying the massive computational and physical costs such mental faculties cost us. For Swinburne, mental activity is "magic!".

    Swinburne also treats free choice as something possible, ignoring the fact that free-action means random-action (which is still subject to some law, since it is subject to some description - albeit a non-deterministic one), and that choice cannot be made except through an algorithm and hence can never be free in his sense. Again, for Swinburne it is as if the mental content just magically "happens", it doesn't count - moral sense, imagnination, memory, reason, all the things needed to make a choice just don't count.

    Finally, it is worth noting that while Swinburne is willing to posit an omni-X god, he isn't willing to posit circular causality. A strage state of affairs. It is true that such a circular causal circle will not provide an explanation for its own existence, but then neither does god according to Swinburne, and indeed to be fair it appears difficult to see how existence can be explained beyond "ultimate" explanations (in Swinburne's terms, an explanation with no "ultimate" unexplained brute facts; Swinburne acknowledges only one type of such an explanation, the "absolute" explanation that takes logical necessity as its foundation, but this is perhaps too rash).

    Swinburne does correctly identify what seperates theism from naturalism - the assumption that there is a person of cosmic importance, a being that the laws of nature (the description of reality) refer directly to his personal properties (such as his will). Naturalism maintains this is an entirely needless assumption with very low prior probability (i.e. plausibility), instead positing uniformity, which is true scientific\epistemic simplicity; but of course Swinburne never confronts that.


  2. Prior probability is rather important in this context (as Yair points out), because there must be a way to distinguish between two hypotheses yield the exact same data.

    For example, take the following two hypotheses:

    1. The sun will rise tomorrow.
    2. The sun will not rise tomorrow.

    In order to affirm number 1 as the best hypothesis *right now*, you need a way to distinguish the prior probability of the two hypotheses. It is plausible that for nature to be uniform/behave regularly is simpler than for it to suddenly change. Ergo, it has a higher intrinsic probability.

    As for no mind being simpler than one mind - this is not so in the case that there being no mind (i.e. God) leaves much more unexplained than there would otherwise be unexplained. In the case God exists, his existence is unexplainable. But in the case that he does not exist, as Swinburne will go on to argue, ther are a great many facts about the world which will then go unexplained. Thus, the alternative is _much_ more complicated than theism, since it entails labeling many entities as your brute facts, rather than just one.

    Also, the sum of all hypotheses which are not theism is not itself a hypothesis which is a believable alternative. To talk of its intrinsic probability is therefore meaningless.

    I had not noticed one of the quotes above before. Swinburne says that a being must know the consequences of its actions in order for it to know that it will realize its intentions. This seems quite incompatible with Swinburne's open theism (the view that God does not know the future).

  3. Philip
    Your example of the sun rising is a good example of a P-inductive argument. As such, it needs nothing of prior probability and it is misleading to talk of probability (prior or otherwise) thin this context. I explained this in the comments on chapter 1.

    Your last paragraph does highlight a significant problem, one which I am aware of and plan to look at in more detail in chapter 6.

  4. Thus, the alternative is _much_ more complicated than theism, since it entails labeling many entities as your brute facts, rather than just one.

    How are any number of brute facts more numerous than infinity? Collecting an infinity of facts into one name does not render them finite. Nor is simplicity a good measure of prior probability - plausibility is measured largely by current knowledge, only secondarily at best by simplicity.

    But it would perhaps be better to have this discussion once the relevant part is reached.


  5. johnathan,

    I explained specifically why you need intrinsic probability in that case. Notice that both theories are completely compatible with either theory. Your missing assumption - which ultimately renders the first hypothesis the better one - is one concerning the theory's intrinsic probability.


    If you would like to argue that God is comprised of an infinity of facts, you will need to explain why this is so, instead of assuming I already agree wth our argument.

    Simplicity is a good measure - since of course you can always come up with an infinite amount of hypotheses to fit the data.

    And plausibility is another criterion I suppose you could suggest, but in so far as we are acquainted with the ramifications of personal explanations, there is no problem in this for theism at all.

  6. Johnathan

    I meant to say notice that the *data* is compatible with both theories, of course.

  7. Being rather simple myself, I would like to start with Swinburne's definition of God. I cannot find any meaning in the words at all. That is I understand the definitions of the words as English, but cannot find that they actually say anything acceptable as reality. As a non-embodied person, which seems to me an impossibility in itself, and he later writes of God as a substance which is contradictory, I cannot see how such an entity, if it could exist, would be able to exert any influence on or over material substance, or any embodied person for that matter. In which case, is it not simpler to dismiss the whole idea as meaningless.

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  9. Jonathan,

    It seems to me that Swinburne led you on a wild goose chaise with this divine simplicity business. It is not the simplicity of some postulated entity within an explanation that is relevant to the prior probability of that explanation - it is the simplicity of the explanation itself. Therefore, it is entirely irrelevant whether or not Swinburne's god is simple in some metaphysical sense. We need to consider the entire god-explanation to see how simple it is (I personally lean towards something like the minimum message length (MML) in evaluating the complexity of explanations).

    The minimal definition of god that you cite here - an omnipotent, omniscient, "maximally free" agent - cannot serve to explain anything at all on its own, not even the fact of the existence of the universe. That is because for S. to be able to say that god would be certain or likely to create this thing or that would mean to infringe on one of these properties: either god created the universe such as it is because he is limited in what he can do, or he doesn't know better, or his choices are shaped by some pre-existing behavioral patterns. Since S. rejects all such possibilities, he has no way to tell what, if anything, such god would create.

    Therefore, in order to provide an explanation ("complete" or otherwise) S. has to either add more properties to god (such as "goodness," which, by the way, would seem to conflict with the "maximal freedom" property, since it amounts to a behavioral pattern) or he has to add brute facts to his explanation in order to account for the existence and the features of the universe that he wants to explain. That is to say, the "complete" explanation would look something like this:

    1. There is a god with such as such properties,
    2. That god created the universe with such as such properties.

    It is easy to see that this god-explanation is not simple at all, for it has to incorporate the description of every single feature of the universe that S. seeks to explain! Moreover, it contains a part that is entirely superfluous to the explanation of the universe: the part that talks about god (1). Eliminating that part and leaving only the brute facts that proclaim the existence of the universe and describe its features (2) would seem to be the most straightforward application of the Occam's razor.