Thursday, October 1, 2015

On the "Myth" that Science Can't Prove Anything

It's pretty common in the world of religious apologetics to act as if any and all uncertainty is inherent room for God.  Belief in a god, is, after all, a philosophy of ignorance, and that type of argument is a popular form of the argument from ignorance.  The idea that nothing can technically be definitive or absolute in the realm of science means that a god is still a possibility.  To the religious, even the most remote of possibility is enough to say, "I'm justified in everything I believe."  To the religious fundamentalist, it means "the fact that I'm justified means it's automatically true and you have no right ever to believe anything else."  To the religious extremist, it means "being justified in believing it means it is morally correct to murder you for disagreeing with me."

While it is technically correct to say that science can't "prove" anything in the absolute sense of proof, that leaves out that what is possible on the basis of a technicality alone is not necessarily reasonable.  Still, you will hear the contention that because scientific consensus can, in principle, be overturned, we can't discount any possibility.  In the previous blog entry, I tried to cover the point that nothing is so cut and dry in science as to say anything definitive.  I'm not suddenly contradicting that -- it is still a fool's errand to look for cut and dry in a field where cut and dry can never really exist.  The thing is that that also applies to the "myth" that science can never prove anything.

Of course, there's a reason that I put "myth" in quotes.

There are countless examples in which the tales of science involve revolutions, and likewise, plenty of stories where previously existing scientific consensus gets overturned.  Nearly every scientist will tell you that we never assume that anything is right and operate on the possibility that everything we know could be untrue.  I recently took a class that kind of involved bringing a lot of hard science to sociological questions that had previously been ill-studied and that really resulted in turning a lot of common beliefs on their head.  Things like that give the impression that scientific consensus is a terribly fragile thing, and it's really not.

I should be clear here, that the propositions that cannot be absolutely proven are the models that we work with.  There are, for instance, people in positions of absolute political power over entire nations who still reject germ theory.  The fact that microbes enter and attack our bodies is not something that is amenable to proof or disproof -- it is the directly observed data...  that is not open to debate under any circumstance because it is the raw observation.  Even the climate change deniers, young Earth creationists, etc. will not only reject the model, but even deny the data itself.  That, at least, is an absolute wrong, as it is denying the very facts on which the science is based.  But even otherwise, that's not what we get at when talking about how science can't prove anything.  The scientific method doesn't simply seek to find out data, but to explain why the data is what it is, and that can only technically be "not disproved," though we have to remember that models are "not disproved" because everything still fits the model.  It's worth pointing out, though, that science can disprove things, and do so conclusively.  So, when we say that the "science is definitive" on something, that can technically be an absolute truth if we're talking about something being proven false.  "Definitive" when it comes to showing something to be true, however, is... not so definitive.

What we have to take into account is the level of support for what is in the scientific consensus and the context in which evidence comes into play.  Take for instance, evolution, which creationists love to pretend is on shaky ground.  Their standard tack is to take some individual datum -- in all cases false and/or falsified data, but for the sake of argument, I'll pretend that they actually had something substantial for the moment.  They will take a single datum that does not appear to fall in line with evolution (or at least their deliberately dead wrong definition thereof), and that is proof that you have to throw the entire theory out the window.  It's on some level, a bit of projection because they view their theology as monolithic, and that's how they think everything works.

I think, for example, to the story of General Relativity, which at one point involved a solar eclipse observation in order to measure gravitational lensing by the sun.  There was a lot of tension throughout the scientific community here because at this point, failure to find the distortion (and it was expected to be incredibly tiny) would have meant that Einstein's model of gravitation had no leg to stand on, and yes...  they would have had to throw the not-yet-theory out the window.  If you hear any scientist talk about this, they would have mentioned that this was a rare exception to the rule.  The reason one single failure would have torn down the model is because we are talking about the very first observations of the model's implications to begin with.  At that point in time, there was no data; just thought experiments and the down and dirty mathematics of it.  This is not normal, though.  When we are thinking of scientific models being "proven", it tends to be the stuff that already has a large body of evidence on its side.

I think back to the example of human chromosome #2.  This is one where we saw that the other great apes have 24 pairs of chromosomes, while humans have 23.  The implication of this is that we should have expected to see evidence of a fusion between two chromosomes in the human genome that doesn't exist in the genomes of the other great apes.  If this was not the case, then common ancestry between humans and the other great apes (at least to the extent that humans are technically apes) would have been proven false.  But why should that be so?  Is it not possible that other apes experienced a split between two chromosomes?  Well, maybe, but given the number of species that have 24 pairs and only one among the group (humans) that have 23, it's much more likely that the one with 23 is the odd one out.  In theory, isn't it possible for a chromosome to just disappear?  Well, on paper, sure.  But given what we know about genetics, that is actually impossible.  You can't just take away functional genetic information and expect the organism to still survive.  Now you notice what happened here?  With all these other alternatives, there was other information brought to bare in order to illustrate why they couldn't work and why the only possible implication was the chromosome fusion.  It isn't just about the 24 pairs and 23 pairs, but all the other details we know about the species, all the other information we know about genetics thus far and the respective genomes of the species in question.  All of that is in the context here, and all of that evidence is pertinent, and that's why it has that serious an implication;  You've got a huge amount of information at stake, in effect.

The evidence that got us to the point of accepting common ancestry is pretty large, too.  All the ERVs, all the pathogens, all the structural features, all the 1:1 dead-on gene matching, and also how it differs from comparisons against other species...  It's not that there's one fact that defeats all that data...  It's that all that data necessitates a number of implications, and when something as foundational as having the same basic chromosomes is in question, it doesn't fit because of all the other knowledge we have.  Now of course, we did find that fusion site, and so common ancestry and the identification of humans as a type of ape is still intact.

You might notice, though, that I only said that the absence of such a fusion site would have disproved common ancestry between humans and the other great apes.  I did not say that it would disprove evolution.  Evolution itself is a much larger system that affected a much larger series of organisms.  Finding a flaw in its predictions with regards to humans has no bearing on the common ancestry between dolphins, porpoises, and orcas -- it's just not relevant.  Something as big as evolution isn't the product of just looking at apes and humans.  Evolution was gleaned not because of some similarities or differences, but by looking at several millions of similarities, several millions of differences, across several millions of species, and from all of that information, analyzing the pattern that presents over the aggregate of all these comparisons.  That pattern, by the way, is not the only evidence for evolution, but it is what evolution explains.  The greater body of evidence includes all the computed implications of the model and the verifying of those implications.  Over the past century and a half, there has been more detail and more depth to what we call evolution since it was first published due to the fact that we learned about a massive range of new mechanisms.  All of these things have since been folded into the theory.  There are close to 2 million extant species on Earth right now that are actually classified as well-studied and distinctly identifiable.  Even with a naive understanding, that means at least 2 million data points that are examined to contribute to that emergent pattern of the tree of life.  That's not even counting extinct species or the extant ones we have yet to study in detail (which we estimate at another 5-6 million or so). The point in bringing all of this up is that the scientific theory is effectively the sum of all of that data, information, and amassed knowledge.  In order to tear down the entire theory, you have to tear down all of those facets.  Not one, not some, ALL.

This is the real reason why there are things that can, at least on a practical level, some things are effectively proven.  It's not that it is impossible in principle to disprove, but that it's basically impossible in practice.  You're not going to disprove climate change by citing a single snowfall or a 5-year long short term downward tick, especially not while deliberately ignoring the longer-term global trend.  You're not going to disprove the entirety of evolution by citing Piltdown man alone, and certainly not by leaving out the parts of the Piltdown story in which evolution itself was the reason it was uncovered as a hoax.

When you hear people talk about scientific consensus and how evolution or climate change is not really open to debate, or not disputed, this is what they're talking about.  The massive quantity of evidence is not something you're going to turn over with a single belief, opinion, or citation of error.  The people who think otherwise refuse to accept the very existence of that evidence or are simply ignorant of it.  Let's also remember that quantity and quality of evidence both count.  The Big Bang, for instance, has one (out of countless many) line of support from the cosmic microwave background.  What's significant about this particular piece of evidence, though, is not just that the prediction fit the data, but that the prediction fit the data so incredibly well that the the error between the observed data and the prediction is too small to visualize.  That kind of precision, specificity that no alternative could be offered, and the fact that no competing hypothesis could offer the same prediction is why the Big Bang has to be taken seriously.

There are times when the old views of science are apparently torn down, and it generally falls into three main categories -- 1 ) there really wasn't a lot of hard detailed proper scientific work on the subject in the first place, 2 ) the public understanding of what actually was accepted science was flawed or 3 ) new research was reported as a revolutionary insight but wasn't actually all that revolutionary in the larger context.  Ninety-nine times out of a hundred in this day and age, it's one or both of the latter two.  The first tends to be more of what happened in the history of science when we look at centuries-old science (or complete lack thereof) compared to up-to-date theories.

For all that, you do hear the quip about hypotheticals that can unravel an entire theory.  In his debate with Ken Ham, Bill Nye famously pointed out that something like a fossil in the wrong rock layers would suffice to change his position on evolution.  This is a more apropos generalization of Haldane's semi-humorous quip about "fossil bunnies in the Precambrian."  This sort of a scenario would have that kind of effect not because it is a large quantity of evidence, but because it would result in a modification of something so fundamental as the tree of life itself -- the very thing that evolution is intended to explain.  But while that makes for an easy target for a hoax, it's also a pretty unrealistic outcome as far as a genuine result.  Even if there was some real example of this, it would be more than fair that it be met with considerable skepticism simply because there would be so much already confirmed data that stands against it, but that would be allayed in time.  But at the same time, the fact that there is so much confirmed data that stands against it means likewise, that it's an inordinately unrealistic outcome.

All said, the science deniers are welcome to try...  What they're not welcome to do is behave as if they're getting anywhere.  It took us centuries of research, thousands of volumes of peer-reviewed literature, studies, meta-analyses, testing of predictions, basic research to learn new things, retrofitting of the models, to get us where we are now.  If you don't like the outcome, tough luck.  You need to put out at least 1% of that quantity of contrary evidence in order to even be worthy of opening your mouth.  Better get busy.

No comments:

Post a Comment