I came across a curious book by Marvin Bittinger, a mathematics educator, called The Faith Equation: One Mathematician’s Journey in Christianity. I’m a sucker for books like this, which seek to prove various metaphysical propositions using probability. None of them are in the least convincing, but I can’t help but be fascinated.
Why? Well, though it’s possible to be uncertain of a metaphysical proposition, just as it’s possible to be uncertain of any physical one, with physics we know we’re in the realm of the contingent where much, most, or even all certainty is denied to us. But in metaphysics, the only satisfying argument is one which ends in truth or falsity. The indifference found in statements like “God might exist” or “God probability doesn’t exist” is dismaying. A question that important should have a definitive answer.
Which it does, incidentally. God’s “existence” is well proved via more than a dozen different arguments, all metaphysical, starting with true premises reaching valid conclusions leaving no uncertainty. But don’t let’s fight over these today, else we will get lost.
Bittinger says that once we accumulate a number of fulfilled prophecies, each of them amazingly unlikely, the probability for God’s existence must be high. What’s a prophecy? “[A] prediction of the future, typically a promise made by God through his prophets.” He adds, “If thousands of these promises are fulfilled, it is incredible evidence of the Bible’s reliability.”
This isn’t a rigorous definition. As the Catholic Encyclopedia says, “St. Paul, speaking of prophecy in 1 Corinthians 14, does not confine its meaning to predictions of future events, but includes under it Divine inspirations concerning what is secret, whether future or not.” Plus, some prophecies are conditional, “Do X else Y”; if X is done, no Y. Is the prophecy then fulfilled? Well, yes, but understanding the outcome isn’t simple. Other prophecies are highly allegorical, so to speak. Just think about the book of Revelation.
Bittinger chose nine prophecies because, he claims, they “lent themselves to estimating, or reasoning, a probability.” All of these have been fulfilled and so now, he says, “have a probability of 1.” This is true: given that these events happened, the probability that they happened is indeed 1. But he’s concerned about the probability of these events before they happened.
What could that mean? On the 13th of April the Detroit Tigers played the San Diego Padres. Tigers lost (don’t weep). The probability the Padres won is therefore 1. But what was the probability they were going to win? There is no unique answer to that question. It is ill posed. All probability is conditional on the information supplied or evidence used. What evidence is the right or correct evidence? Historical record? This season’s outcomes? Player stats?
There isn’t any “right” evidence, though there is a sense there exists a best evidence. But learning that best evidence isn’t always possible, especially in fluid human events like baseball games. Sometimes we can know something like the best, but only in highly controlled situations. Think experiments with inclined planes or electrons.
Now given any set of evidence, a probability can be had. Not necessarily a numerical probability. If the evidence about the ball game was just this: “Them Padres are lookin’ good. And the Tigers relief maybe ain’t so hot” there is no numerical probability possible. Yes, people can state one, but they are not doing so based on the this evidence.
The first prophecy Bittinger uses is “Israel’s Messiah Will Be Born in Bethlehem” from Micah 5:2. He gives this a 1 in a million shot. How? Firstly, he went to trouble to figure the number of villages in which Jesus could have been born. About 1,000. Second, he figures the chance the prophecy would have been fulfilled 700 years after the prediction was made, which has the probability, he says, of 1/(2*700), a figure he generates using something called a “time principle.” These two probabilities are multiplied to get a number which is less than 1 in a million.
He does similar things for eight other prophecies arriving at the cumulative product of 10-76, which is mighty small. Therefore, and considering there are many more than nine prophecies in the Bible, mathematics shows God exists.
See what I mean? Unsatisfying in the extreme. I feel for Bittinger. He and I are fellow believers, and we agree with the prophecies. But I can’t agree with his arbitrary quantification. One reason is metaphysical. If the prophecies were unconditional, in the form of “X will happen”, then given (at least arguendo) the best evidence “God said X will happen and what God says goes”, then the probability of “X will happen” equals 1, a number with which even atheists would agree.
On the other hand, to the man who does not accept the “God said, etc.” premise, the before-the-fact prophecies are uncertain. And their fulfillment does given evidence to the hypothesis God exists. But it can never be conclusive evidence because the probabilities for fulfillment are not unique. Endless possibilities for disagreement about historical events exist.
Update If you want the best of the best of these probability arguments, check out (the start of) one by Richard Swinburne: Swinburne’s P-Inductive and C-Inductive arguments (for the existence of God). Another not so great: Bayes Theorem Proves Jesus Existed And Did not Exist.