The “Intrinsic Probability” of Theism

Before coming to the evidence for the existence of God, a preliminary question needs to be asked: How plausible is it, a priori, that God exists?

Consider the case of John and Jane. John assumes that the existence of God is profoundly unlikely and therefore views theistic proofs with deep suspicion and finds them unpersuasive. Jane, on the other hand, assumes that the existence and nonexistence of God are about equiprobable and therefore views those same proofs with an open mind and finds them persuasive.

The point is that our presuppositions about the “intrinsic probability” of theism (where the “intrinsic probability” of a hypothesis is a measure of its simplicity prior to the evidence) are crucial to the outcome of any discussion of evidence for the existence of God and so need to be taken into account. [1]

It is at first tempting to think that John is correct. The existence of God seems about as improbable as anything can be. God, if he exists, is unlimited: infinite in power, knowledge and love. The principle of parsimony, which recommends the simpler of any two competing explanations, would seem to recommend an atheistic explanation in every possible case: Whenever there are two possible explanations for the evidence, one which appeals to the existence of God and one which does not, the explanation which does not appeal to the existence of God is simpler and therefore has greater intrinsic probability. Prejudice against theistic claims is, it seems, justified.

However, in The Existence of God, Oxford professor of philosophy Richard Swinburne presents a strong counterargument to this view. He first notes that to postulate a limited force is to postulate two things: The force and whatever constrains it; while to postulate an unlimited force is to postulate one thing: The force, which, being unlimited, is not constrained by anything. “For this reason,” he continues, “scientists have always favoured a hypothesis ascribing zero or infinite value to some entity over a hypothesis ascribing a finite value when both hypotheses are compatible with the data.” Thus, “the hypothesis that some particle has zero or infinite mass is simpler than the hypothesis that it has a mass of 0.3412 or a velocity of 301,000 kilometres per second.”

Theism is the proposition that the ultimate explanation of the universe is a single immaterial person that is of the simplest kind imaginable because it is unlimited: Since a person is, “a conscious entity that has rational thoughts, moral awareness, intentions, continuity of identity and who is able to perform basic actions,” a person having zero powers would not be a person at all. [2] And so it follows that in postulating a person with infinite powers the theist is postulating the simplest person logically possible.

The intrinsic probability of theism is therefore high and prejudice against theistic claim unwarranted.

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[1] Some philosophers do not recognise the concept of “intrinsic probability.” Plantinga, for example, thinks it is doubtful that there is such thing as intrinsic logical probability but concedes that, “we certainly do favour simplicity and we are inclined to think that simple explanations and hypotheses are more likely to be true than complicated epicyclic ones.” The reader who shares this view can simply equate “intrinsic probability” with the notion that, all things being equal, simpler hypotheses commend themselves over complex ones.

[2] As Dallas Willard notes in The Divine Conspiracy, “Any being that has say over nothing at all is no person. We only have to imagine what that would be like to see that this is so. Such ‘persons’ would not even be able to command their own thoughts. They would be reduced to completely passive observers who count for nothing, who make no difference.”

 

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