Is there really a 67% probability that God exists? - Document (2024)

Date: Summer 2004

From: Skeptic (Altadena, CA)(Vol. 11, Issue 2)

Publisher: Skeptics Society & Skeptic Magazine

Document Type: Book review

Length: 2,369 words

A review of The Probability" of God: A Simple Calculation That Proves the Ultimate Truth by Stephen D. Unwin, Crown Forum, 2004, 259 pp, $22.95 ISBN 0-7615-2684-0

THE PROBABILITY OF GOD IS A wonderful yet deeply flawed book. Physicist and risk-analyst Stephen D. Unwin uses a statistical method called Bayesian analysis to conclude that there is a 67% "probability" that God exists. The book is thought-provoking and written in a witty and engaging style. I found it impossible not to enjoy reading it.

The "evidences" pro and con as identified by the author are:

1. The recognition of goodness

2. The existence of moral evil

3. The existence of natural evil

4. Intra-natural miracles

5. Extra-natural miracles

6. Religious experiences

These are all hotly disputed topics in theistic debates, so clearly there is nothing particularly significant about the author's 67% figure. The number is subjective and reflects the author's particular sensibilities rather than some measure of reality based on empirical facts. The reader will arrive at the 67% figure only if he happens agree with all of Unwin's assumptions, arguments, and evaluations of the "evidence" as identified by him. The author calculates his personal confidence level and nothing more.

He explicitly tells us this on page 63: "In the Bayesian world, this is precisely what a probability represents: a degree of belief or level of confidence that some proposition is true." And on page 131 he states, "Well, let's not forget that this number has a subjective element since it reflects my assessment of the evidence. It isn't as if we have calculated the value of pi for the first time. Nevertheless, it's my best attempt, it was based on systematic analysis, and you know how I got there."

Therefore the subtitle of the book--"A simple calculation that proves the ultimate truth,"--is pure fluff intended to sell books. A more serious problem with the work is that the author attempts to begin from a position of ignorance to prove the existence of a god (p. 4), yet he arbitrarily limits consideration only to his concept of the Judeo-Christian god. On what bases are all other god concepts excluded? Special pleading leads to a fatal skewing of the numbers towards the author's pet concept. This forms the core of Unwin's book.

Through special pleading, Unwin begins by invoking an a priori 50% probability towards his god's existence by arguing that 50% is an expression of maximum ignorance (p. 58). I found this position astounding. What of other speculations? Are we merely brains in vats hooked to computers? Do magic elves steal socks from the dryer? Do Space-Penguins live in the center of the Moon? To be consistent the author would also have to assign an a priori 50% probability that each of these claims is true.

If we begin with the acknowledgment that we are ignorant as to which, if any, of the potential god concepts might actually be true, then there is no basis to favor one concept to the exclusion of all others. Thus all...

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