David Hume and Lawrence Shapiro get it wrong on miracles

I really don't like Hume-- really don't like him. Hume was a closet-atheist-sophist, a triad of my least favorite things. The damage he has done to modern clear logical thought is incalculable.

Philosopher Lawrence Shapiro from the University of Wisconsin, Madison (where else?) picks up Hume's mantle, and repeats Hume's idiot argument about justification for belief in miracles.

Shapiro believes that we never have justification to believe in miracles. From Shapiro's essay, with my rebuttal:

[W]e can all agree that miracles such as Jesus rising from the dead either did, or did not, occur. My claim is that, to date, evidence for such an event — and any other event that is regarded as a miracle — is too weak to justify anyone’s belief in it as fact. 

I claim no great originality for my argument. I’m borrowing from the great Scottish philosopher David Hume, particularly Section 10 of his magnificent Enquiry Concerning Human Understanding (1748). If there is any novelty in my presentation, it owes to the marriage of Hume’s ideas with a famous theorem in probability theory proposed by the Reverend Thomas Bayes in ‘An Essay towards solving a Problem in the Doctrine of Chances’ (1763). The technical details, fortunately, can be put to the side for our purposes.
The argument begins with an assumption that is very favourable to those who believe in miracles. Let's say that the witnesses of miracles are very reliable — far more reliable than ordinary witnesses. This is not to say that miracle witnesses are infallible. If they were, then of course we could trust their reports and there would be nothing more to discuss. But witnesses, we know, are never perfect. Things aren’t always as they seem, our eyes on occasion mislead us, and sometimes we see what we want to see. When a courtroom drama hinges on a witness who turns out to have identified the wrong person, no one doubts that such misidentifications are possible. 

Even so, for the sake of argument, let’s suppose that witnesses to miracles almost never err. Of all the reports they make in the course of their lifetime — hundreds, thousands, even 100,000 — they make only one mistake. Should we believe someone who claims to have witnessed a miracle if his or her testimony has a chance of only one in 100,000 of being wrong? 

Now I want to consider a slightly different question, albeit one that will have lessons for how we should answer the question above. Suppose you visit your doctor for a routine check-up. After testing a sample of blood, the doctor grimaces. ‘I have bad news for you,’ he says. Bad indeed. You’ve tested positive for a very lethal form of cancer. Your chance of surviving the next three years is practically zero. A treatment exists, but it carries significant costs (blindness, incontinence, all your hair falling out). Furthermore, your doctor says, the test is very good. In every 1,000 tests, it gives only one false positive – that is, a diagnosis of cancer to someone who doesn’t have the disease. Also, 0.001 per cent of the time it goes wrong the other way, giving a negative result to someone who really does have the disease. Do you opt for the treatment? 

The correct answer is this: before deciding, you need a piece of information that the doctor did not provide. Without information about the base rate of the disease – its frequency in the population at large – any facts about the reliability of test are completely useless. 

To demonstrate this, let’s first suppose that the cancer is not terribly uncommon. Perhaps it affects 0.001 per cent of the population. This means that, for every 1,000 people in the population, one person will have the disease. We also know that the test goes wrong 0.001 per cent of the time. That is, it errs one time in 1,000, and it errs in two ways. If we select 1,000 people at random from a larger population, one person in this group who is actually healthy is likely to test positive for cancer. However, the chances are that this group also contains one sick person, because the base rate of the disease, as we’ve said, is one in 1,000. Yet, because the test fails to detect cancer only one time in 1,000, chances are very good (999/1,000) that the test will correctly identify the sick person in the group. This means that, having tested 1,000 people, our test ends up ‘diagnosing’ two of them with cancer, when in fact only one of them has it. Given the base rate of the disease and the sensitivity of the test, if you’ve tested positive, the chance that you are actually sick is only 50 per cent. 

An obvious but interesting conclusion follows. If we hold the accuracy of the test constant but decrease the base rate of the disease, the trustworthiness of the test result diminishes accordingly. For instance, let’s now suppose that the base rate of the disease is one in 10,000. That extra zero means that, having tested positive, the odds of genuine sickness slip down to 10 to one. With its one-in-1,000 error rate, the test will identify 10 people as having the disease when they do not, and one as having the disease when he or she does. Making the disease rarer still, so that it affects only one in, say, 1 million people, puts the chances of illness at a vanishing 1,000 to one. So, this test of ours turns out to be no good at all when the disease for which it tests is rare.

This reasoning would be appropriate to a medical screening test used for people at random, in which there is no reason to believe that a particular disease is present.

But the appropriate analogy to a Christian belief in the Resurrection is not a medical screening test. That is, that Christians are not beginning with no reason to believe the Resurrection is true. Belief in the Resurrection, for a Christian, is belief in one aspect of a truth that has many facets and extensive confirmation in myriad aspects of their lives.

The analogy to a Christian belief in miracles is that of a patient who goes to a doctor with fever, unexplained weight loss, spontaneous bleeding, anemia, swelling of lymph nodes, and recurrent infections, who has a blood test that shows acute myelogenous leukemia. While AML is rare (incidence 1/20,000/year) and the diagnostic test probably has an error rate of at least 1/1000, the likelihood that the patient has AML is very high, and the patient would be a fool to believe that because of the incidence of the disease and of the error rate of the test that the positive result is almost certainly an error.

If Shapiro were a doctor, and told his patient not to worry about the test result, he would loose his medical license. Too bad he doesn't have a philosophy license he could lose.

The reason that the diagnosis is almost certainly true is that the prior probability of a serious hematological disorder is quite high given the patient's presenting symptoms (fever, weight loss, spontaneous bleeding, anemia, etc). The test and the frequency of the disease must be considered in context.

The same is true of a Christian's belief in the Resurrection. The Christian belief that Jesus rose from the dead is not an isolated belief, as it would be if the Christian believed that Joe Smith rose from the dead 2000 years ago, based on a few old books. The belief in the Resurrection is but one (essential) part of a Christian worldview, predicated on life experiences, study of the Bible and of theology, prayer, etc.

I believe that Christ rose from the dead because I have met Him (in prayer, in bible study, in my daily life, in my work...). Whatever confidence an atheist like Shapiro may place in my experiences, I am most certainly not accepting Christ's Resurrection as screening test: "gee- I wonder how likely the Resurrection of one guy in 100 billion is, based on a few 2000 year-old books?"

Lawrence digs a deeper hole:

The practical lesson is this: knowledge of the rate at which a test errs tells you nothing by itself about whether the test results should be trusted. You need also to consider whether the thing for which you are being tested occurs frequently or seldom. If the disease is rare and you test positive, you should look for another explanation for your result than actual illness. Given a test that errs one time in a 1,000 and a disease that is present in only one person in a million, there is a better explanation. Evidently, the test is sensitive to factors other than disease. Something in your blood, perhaps, triggered the positive outcome. This possibility is far more likely than that the disease was responsible for the positive result. Indeed, it’s 1,000 times more likely.

You also must consider the prior probability that the miracle is true. The prior probability of the Resurrection is determined by a host of life experiences and theological insight and insight gained by prayer. For a Christian, belief in the Resurrection is consistent with massive knowledge about God and His grace. Belief in the Resurrection is not a "screening test" performed without any prior knowledge.

Still another point concerns the issue of justification that I raised earlier. Because a positive test result in the conditions I have described is far more likely to be wrong than right, the result fails to justify the belief that you have the disease. Even if you do have the disease, and even if the test correctly diagnoses you as having the disease, you should not believe this on the basis of the test alone. Forget about the test result. It’s as good as worthless as far as justification goes.

No Christian accepts the truth of the Resurrection "alone". The Resurrection is part of a living relationship with the One Who was resurrected.

Lawrence:

Be that as it may, if Jesus’s resurrection is the ‘disease’ and the witness report is the ‘test’, we can now do the algebra to decide whether to believe in the resurrection. The base rate for the resurrection is (let’s say) one in 1 billion. The witnesses go wrong only one time in 100,000. One billion divided by 100,000 is 10,000. So, even granting the existence of extraordinary witnesses, the chance that they were right about the resurrection is only one in 10,000; hardly the basis for a justified belief. 

No one is justified in believing in Jesus’s resurrection. The numbers simply don’t justify the conclusion. But the resurrection is just one miracle. If we suppose that all miracles are similarly rare, then, by parity of reasoning, belief in any one of them is similarly unjustified. As noted earlier, my conclusion doesn’t deny that miracles have occurred or might occur, just that the available evidence fails to justify a belief that they have occurred. So, if you wish to continue to believe in miracles, you must do so knowing that the evidence is not on your side.

The prerequisite for an intelligent discussion of the warrant for belief in the Resurrection requires a genuine examination of the basis for the belief, which includes examination of the broad religious experiences of Christians. We are not doctors screening random patients for cancer. We know our patient intimately. Our belief in the Resurrection is part of a relationship with Christ, a relationship that we experience daily and that has profound ramifications in our lives.

Shapiro, like his mentor Hume, is blinded by atheism. They presuppose an atheist framework for belief in miracles, a framework stripped of genuine religious experience that serves as a predicate for belief in miracles. 

Presupposing naturalism, Shapiro and Hume infer naturalism. Big surprise.

There is another analogy that is much more appropriate to belief in the Resurrection than Shapiro's woefully inadequate cancer screening analogy. Imagine a man who loves his wife and longs to see her when she returns from a trip. He is waiting at the airport to greet her. As she walks out of the gate, he runs to hug her.

But did he have warrant to believe it was her? After all, as Shapiro/Hume would point out, there are seven billion people in the world, so the "screening" likelihood that that one person at the gate would be her is only one in seven billion. And it is certainly possible that the husband could be mistaken by a face in the crowd-- even if it's only one chance in a million that he would misidentify his wife.

By Lawrence/Hume's logic, the likelihood that the husband would embrace the right person is only one million/seven billion= 1/7000, or 0.014%.

By Lawrence/Hume's logic, the husband has virtually no chance of hugging the right person, his beloved wife.

But that's nonsense. The truth is that the husband knows his bride intimately, as she knows him, and he knows where and when to expect her, and he has faith that she will be there to embrace him at the airport gate. He is sure that he is embracing his beloved.

We Christians have such faith in our Beloved as well.

The Humean rejection of warrant for belief in Christian miracles, which has had enormous influence on our degenerate culture, is moronic junk philosophy.

Romans 1:22.