A certain fundamentalist I know, apparently exasperated because he was unable to convince me of the superiority and infallibility of his religious convictions, once asked me just what kind of proof I would accept, anyway. (Ironically, he’s one of those individuals who demand scores of “sources” when presented with an inconvenient fact that clashes with his ideology, even if verification would require less than five minutes of Googling.) This is a query I’ve found myself pondering for several reasons — not just specifically what kind of proof I would accept about religious beliefs, but about postulates of any kind.

First of all, the question almost turns the burden of proof on its ear. It’s not my job to detail in advance what kind of proof I would deem acceptable for various propositions. The real question is, what have you got? If you want me to believe what you believe, you need to present your case, and then I’ll worry about evaluating it — assuming it’s actually worthy of evaluation. Like it or not, the burden of proof is always on the believer.

Furthermore, depending on the specific premise you wish to corroborate (more about this shortly), it might even be impossible to specify in advance what kind of substantiation would pass muster.

Consider the biblical account of Moses parting the Red Sea. What kind of proof could possibly satisfy the skeptic about that incident? Forget that it was attributed to Moses; forget that it was reported in the Bible. How would you go about proving that anyone had accomplished such a feat? Since there’s no verified case of anyone doing so (well, except for Cecil B. DeMille) there are no benchmarks for determining authenticity. An unedited, non-fake video of the event might suffice. Good luck locating one of Moses performing the stunt.

Still, it’s a fair question in a sense. While we may not always know what specific proof of a belief would be acceptable, we can at least lay out some guidelines for evaluating such proof. So let’s do that now.

1. Proof Or Evidence?

When people talk about proof, they usually mean evidence. There’s a difference. Proof can be replicated, but evidence is the footprint of something that happens only once. It’s very hard to prove most things outside a laboratory, but we often can stack up enough solid evidence to consider the proposition proven for all practical purposes. The problem is that people quite often (like the fundamentalist in question) have misconceptions about what quantity and quality of evidence are adequate.

2. What Are You Trying to Prove?

It should go without saying that if you’re attempting to prove something, you should be clear about what you’re trying to prove. But this is a point that many people get muddled about — even scientists are occasionally guilty, as we’ve previously noted in discussing a couple of studies.

One of them found a link between happiness and marriage, which led people to conclude that getting married makes you happier. But it turned out that this was confusing correlation for causation — or more accurately, reversing cause and effect. Another much-touted study found that moderate drinkers lived longer than teetotalers; from which many people concluded that moderate alcohol consumption is actually beneficial for your health. But researchers failed to consider that their sample of abstainers included individuals who formerly had been heavy drinkers, and had quit because booze was damaging their health. When these folks were filtered out, the “benefits” of drinking evaporated like alcohol. While these two studies established significant evidentiary links, they did not prove that marriage makes you happy or that booze makes you healthy; those are false inferences.

This fundamentalist cited a couple of historical sources who mentioned Jesus as “proof” that biblical accounts of Jesus must be true. (In fact, historical evidence for the existence of Jesus is very flimsy at best — which is especially noteworthy considering what an extraordinary life he was supposed to have lived. But that’s a story for another day.) But these were non-contemporary writers, not eyewitnesses; and their fleeting mention of Jesus merely indicates that they had heard rumors about him, not that those stories were true. Even if we grant that there really was someone named or resembling Jesus, that does not in any way validate the supernatural claims about his life and deeds. And the veracity of those narratives doesn’t necessarily impact that of other biblical claims. Which brings us to the next point…

3. Dependent or Independent

One mistake people often make is confusing dependent trials with independent trials. Gamblers, especially novice gamblers, have been known to learn the difference the hard way. Card games revolve around dependent trials; every time a card is removed from the deck it alters the probabilities for those cards remaining. (Hence the practice of “counting cards”.) But in most games of chance, independent trials rule the day; having the roulette wheel spin black 50 times in a row does not make it one whit more likely that the next spin will be red. The odds never change. And, as the saying goes, “the dice have no memory”. Furthermore, no matter how mathematically probable it is that an event will occur, or that a proposition is true, the probability should not be construed as proof of certainty.

Science and math are built upon dependent trials. If you propose a scientific theory about the behavior of atoms, it’s necessarily founded on the proposition, verified long ago, that atoms actually exist. Geometry entails constructing proofs of theorems, using the building blocks of theorems already proved and/or self-evident axioms.

In history, and by extension in religion, the distinction is often murkier; but it’s no less crucial. Knowing that a farmer lived in Alabama during the Civil War era on a plantation his family had owned for generations certainly makes it extremely likely that he was a Confederate sympathizer. But you can’t say you proved it unless… well, unless you have some proof.

Knowing that the Israelites spent many years in Egyptian bondage may make it somewhat more likely that there was a tribal leader (call him Moses if you must) who locked horns with a pharaoh. But it doesn’t prove any such thing conclusively. And it certainly doesn’t prove that Moses and his followers combed their way through an obliging body of water without getting a stitch wet. Furthermore, even if we somehow could establish that such an event really transpired, that would not necessarily vouch for the truthfulness of any other biblical tales. For the most part, they should all be regarded as independent trials. (One of the problems with religious arguments like Pascal’s Wager is the implied false presumption that the truth of one religious proposition would guarantee the truth of all the others.)

4. Accentuate the Negative

While it may be very difficult to verify that a proposition is true, it’s often easier to prove that it isn’t. And although failure to disprove something does not indicate that it must be true, success in disproving something can save a great deal of time and effort in struggling for affirmative proof. That’s why scientists make an issue of “falsification”. Philosophers refer to it as the black swan principle; you can’t prove the conjecture that all swans are white because it would involve examining every swan that ever existed; but you can disprove it if you can track down one single black swan.

Going back to “scripture”, one episode that is easily falsified is that in which Joshua causes the sun to stand still so his army can continue wreaking bloody havoc against the enemy in broad daylight. This is impossible because it’s nonsensical: the sun, of course, does not really “rise” and “set”.

But let’s cut the Old Testament author of this narrative a big serving of slack, and suppose that he actually knew better, and didn’t intend to be literal (even though fundamentalism is, in fact, based on reading the Bible literally). Let’s assume that, being divinely inspired and all, he understood science even though science hadn’t been invented yet. Say he was really just using poetic license, or speaking in terms his readers could relate to. Assume, in other words, that he really meant to say that the earth stopped turning so the sun would appear to stand still. What kind of evidence would such an occurrence leave as a footprint?

The answer is, absolutely brutal. There would have been instantaneous global devastation on a scale one can hardly imagine. If you think the asteroid that killed the dinosaurs was bad, you ain’t seen nothing. Should the earth suddenly stop spinning, everything on it would continue moving, at speeds typically around 1000 mph. That includes rock, water, buildings — and human beings. There would be few if any survivors — such a cataclysm probably would cause the extinction of all life on the planet. The best case scenario would be that a scant handful of humans would survive — in which case the population of the earth would be far smaller than it is now. But since we are all here, and there are no signs of worldwide upheaval mere centuries ago, it’s obvious that global rotation has continued unabated.

In other words, we know the story is false, at least on a literalist level. (Did the author just mean that Joshua inspired the warriors with such devotion to their slaughters that it felt as if time stood still? Who knows?) And since we know that this one biblical tale is false (and it’s hardly the only one) we can, courtesy of the black swan, conclude that the premise of biblical inerrancy is also false.

5. Alternative Facts

But let’s imagine that we did have evidence of such devastation. Suppose that there were definite signs of global upheaval from a couple of millennia back. Suppose, moreover, that we were no longer around to witness it. That would certainly prove to us extinct critters that the Joshua tale was true, wouldn’t it?

Well, no. Not by a long shot. Because those results might have been produced by other causes; indeed, by a virtually unlimited number of causes. And this is true regardless of whether there is a divine hand guiding the cosmic forces involved.

We must be careful not to fall into the fallacy of single explanations. When scientists determine that Factor A produces Result B, they have conducted rigorous experiments to eliminate other possible explanations. Unless we perform a comparable exercise, we shouldn’t conclude that we have proof. In order to prove the accuracy of a claim, biblical or otherwise, we must not only authenticate the evidence, we also must rule out other possible explanations. And that’s often a very tall order indeed.

Look, there’s a reason it’s called faith. If you’re a believer, then believing is what you do. You must trust that somehow the difficulties and contradictions can be resolved, even if you don’t understand how. If, on the other hand, you’re a person who doesn’t believe anything without sound proof, then perhaps religion isn’t for you — at least not without some major modification or adjustment.

In any case, you can’t have it both ways. It does not compute to say, on the one hand, “I believe the earth was created in 6 days because the Bible says so”, and on the other hand, “I refuse to accept climate change because I don’t trust scientists”.(No, it’s not equally inconsistent to do the reverse, accepting science and rejecting religion, for at least four reasons. (1) Science is not built around a central authority. (2) Science constantly evolves and makes adjustments for greater accuracy. (3) Scientists form a vast network of checks and balances. (4) It’s simply not the same species of “belief”.)

And yet that’s exactly what all too many people do.