What is the message that defenders of science broadcast to the doubtful and the faithful? Usually it sounds something like, “You must accept theories that explain the evidence.”

But I wonder what message is actually being heard.

Advocates for scientific theories, such as evolution, proudly point to all the evidence for that theory. “Look how evolution can explain our genes, our bodies, and our collections of fossils!” The ability of a theory to explain all that evidence, maybe every item of evidence, must be impressive to any rational mind. And so it is — the way that a theory is compatible with all the gathered evidence could only be dismissed by a confused or dogmatic person.

But there are many intelligent religious people, who are only too happy to apply this standard of evidence to the God Hypothesis. The faithful are being told by preachers and theologians that only God makes a good fit with ALL of the evidence — the whole world itself! If the standard for a good theory is simply that it fits all of the evidence (as pro-science voices say all too often), then the God theory is even better established than any scientific theory! Sure, cramped fundamentalisms ignore the evidence and get their deserved refutations, but modernist liberal theologies intelligently design their God. This New God uses nature and scientific laws to fulfill the Divine Plan. No matter what happens, either God did it, or God allowed it to happen.

We’ve encountered religious minds that are closed to evidence. But here we are talking about minds that are too open to too much evidence. No matter where these religious people look, they think that they can see the hand of God involved. When dealing with such folks, complaining that there is no evidence for God just isn’t going to impress them at all. Modern theologies have carefully crafted gods that do fit all the evidence. For example, such believers have no problem accepting evolution, and they can easily brush off atheist demands for miracles on command. Treating all religious believers like they are just Biblical literalists or conservative fundamentalists won’t be working anytime soon.

Maybe the message to such liberal believers should instead be, “No, no — Don’t believe a theory just because it fits all the evidence.” But now there are two opposite messages to use: when addressing fundamentalists, tell them to believe the theory that explains the evidence; when dealing with liberals, tell them not to believe a theory that explains all the evidence. Can secularists send out contradictory messages, sometimes? Perhaps. Evidently some third consistent method of demanding respect for evidence is required.

We need a more careful approach to dealing with religious belief. Simply accusing all religious believers of ignoring evidence and dismissing science is not a reality-based strategy. Something far more complex is going on, and defenders of science have to be more mindful of how religion works. As social and cognitive sciences have been saying for a while, religion is actually designed to avoid confrontation with the observational evidence. Religion takes advantage of many brain centers simultaneously, from those dealing with emotion and drives to those handling morality and sociality. Debating against religion is far more than just throwing evidence and science at religious belief. If just the physical evidence and science did the job, then books defending atheism would look just like a science textbook. Evidently, that is not the case. (My new book The God Debates joins an impressive atheist lineup of works far more potent than any textbook.) Science and religion are actually designed to do quite different things. Here we shall speak of religions that suppose that the paranormal or supernatural have living qualities — some religions, like parts of Buddhism and Taoism, instead treat the divine as impersonal.

Science: Science postulates habitual impersonal forces to explain patterns in the environment. These postulates can be tested against further empirical consequences in the future. Natural forces obey laws that are always valid and never change. The scientific aim is to build up a coherent system of knowledge about how the world works.

Religion postulates unpredictable willful agents to “explain” particular extraordinary events. These agents cannot be tested by anything that happens in the future. Gods demand obedience to divine laws, but they can abruptly change the laws and mysteriously change their minds at any time. The religious aim is to build up a communal body of believers that fears God to make them work better together.

Now, notice how religions rely on unpredictable agents — no matter what actually happens, a believer can always figure that “God just mysteriously wanted it that way.” A supernatural God like that is entirely impervious to any evidence. Nothing that happens could prove that God doesn’t exist. Even the problem of evil can be handled by a sufficiently stubborn (and hard-hearted) believer. Theologians are fond of claiming that this satisfactory relationship to all evidence is further proof of God. When the faithful hear pro-science people say, “Only believe on enough evidence,” they can conclude that their faith is entirely reasonable. Religion creates such an all-encompassing worldview complete with intense emotional and social attachments in order to account for anything that might happen to a believer.

What is the best argumentative strategy now? We should accuse religious believers of irrationality precisely because they want all possible evidence to fulfill their God hypothesis in advance. Science doesn’t work that way — a scientific hypothesis tries to fit ALL relevant evidence gathered so far, AND it tries to predict new evidence that hasn’t been gathered yet, AND it admits inadequacy if new evidence does not fit it. That’s how a genuine hypothesis works — religions can’t even offer hypotheses, much less good hypotheses. At most, they offer rationalizations for God, that fail to even square with basic rationality .

Science orients belief to the way nature works; religion orients believers to working with God. Religion’s irrationality is not ultimately about its stubbornness against to evidence, but its eagerness to see all evidence as evidence of God.

I have heard some friends of science try out a smarter strategy for demanding fidelity to evidence from the religious. Recently I received an email inquiry asking me to comment on this proposition:

“Something is falsely held to be true until there are conditions that could determine it false.”

Rhythmic, catchy in a way — but accurate? Let’s explore this proposition a bit.

It reminds one of this proposition:

A. “A proposition for which there are no falsifiability conditions is unscientific.”

and also this one:

B. “You should not believe that something is true unless science has confirmed it.”

Combining these two propositions A and B, you arrive at the judgment that

C. “You should not accept as true any proposition that lacks falsifiability conditions.” Not as catchy as the first version, yet it captures its literal meaning.

Now, is this proposition C valid and wise? (Note that we should NOT should ask whether C is true, because that would result in a weird self-contradiction — according to C itself, C should not be accepted as true, as it lacks falsifiability conditions. C is a philosophical judgment, not an evidentiary observation or a result of scientific inquiry.)

To judge C, we can examine its components A and B.

A is not quite right — Popper’s view on scientific method is no longer the gold s

tandard of how science actually should work. Another view has prevailed, from Dewey and Quine and Kuhn, that scientific paradigms are large systems of theoretical propositions that include mathematical, logical, and axiomatic principles that themselves lack falsifiability conditions. Furthermore, a new theory is granted provisional scientific status even if no one can think of direct empirical testing for it, so long as it suggests how to resolve puzzles with established scientific theories (e.g. string theory). But in the long run, that theory will be sidelined if no direct or indirect confirmation by evidence seems ever forthcoming.

B is not quite right either. People rationally believe all sorts of things that science has never and would never bother to confirm. Examples: where I parked my car last night, what Mary told me yesterday, how my toothache feels to me, and how to catch a fish. Long before science existed, people were using their ordinary practical knowledge to live. All that “ordinary” knowledge is actually the broad empirical foundation on which science rests, and that foundation existed long before science and will still exist even if humans someday forget all science. That foundational base of broad ordinary knowledge has a different validity standard than science’s — ordinary knowledge relies on community agreement. I continually check what I think I know against what others think too — if no one can confirm what I saw at the football game, then I conclude that my perception may be mistaken. On the other hand, if my beliefs make a good fit with everyone else’s evidence too, then I rightly take it to be justified knowledge. Knowledge by “common consent” is no fallacy, generally speaking. That most or all mankind believes something is a very good reason to accept it, all things being equal, for that is how human rationality works. (We learn how to think rationally by being taught how others think and what others already believe.)

After science was invented, all things were no longer equal. Science supplements ordinary knowledge with vastly improved knowledge, and common consent gets overruled by scientific knowledge. There is a parallel superiority of ethical judgment over the “common consent” of humanity on moral matters — after past experiments with slavery caused horrible consequences for all to see, no society could justify slavery anymore.

Now, where do we stand with “Something is falsely held to be true until there are conditions that could determine it false.” As a general rule, it is unacceptable — it can’t handle what we take to be justifiable knowledge and it doesn’t fully square with actual scientific method. Scientific knowledge is not the only kind of knowledge, it is not built up by taking all the evidence equally seriously, and it hardly tries to do anything like “explaining all the evidence.” A theory compatible with all the evidence is not really supported by any of it. Science works by going out and seeking special predicted evidence that can help with proving a theory wrong, or with preferring one theory over another. Pseudo-science and religion avoid such hard work – in their rush to explain everything, they explain nothing.

Back to dealing with religious believers. Remember that proclaiming devotion to “all” the evidence only delivers the wrong message to dogmatic believers. Only a special treatment of evidence does the needed job of separating good science apart from pseudoscience and religion (I recommend Massimo Pigliucci’s new book Nonsense on Stilts: How to Tell Science from Bunk ). Indeed, proclaiming fidelity to science isn’t even enough to force liberal religious believers to admit that God must go. Religion is designed to do far more, and far less, than science. As a powerful cultural force that grips all the brain’s functions, it will take strong efforts on many fronts to completely dissolve religion away. Defending science is just a start – supposing that our job is done when we defend science is not a reality-based strategy for confronting religion.