UPDATE: Leiter has reposted
a previous item in which he debates the nature of science with me. I concede that Leiter is correct on his main point: It's not that useful to use the term "a priori" to refer merely to scientific (or other) beliefs that are formed based on evidence accumulated at some prior point. As Leiter correctly observes, the "vast majority of the background beliefs and theories we work with all the time" are a priori in that sense.
Nonetheless, Leiter completely misses a point that I made at length. Before I address that point, a couple of brief objections: First, Leiter is twisting the record -- typical behavior where Leiter is concerned -- in suggesting that I am an "apologist" for Intelligent Design. I never said one word that apologizes for Intelligent Design; my observations have always been purely
descriptive, not normative. I already posted about
Leiter's misinterpretation here. Second, why does Leiter mention that I belong to the Federalist Society? I'm not embarrassed by that fact at all, but it is irrelevant here. It would be as if I said, "Apparently intent on demonstrating that people who believe in universal health care are too dense to understand what some scientists have themselves said about the nature of science, Leiter argues that," etc., etc. It would be utterly beside the point.
UPDATE: Leiter has updated his post to correct his two mistakes above. But he still has no response whatsoever to the main point (which I address below). He's had several opportunities by now to explain what scientists mean when they rule out the supernatural "by definition," but he still refuses even to attempt an answer. If Leiter, of all people, is speechless, he obviously means to concede the point.
Leiter also claims that I have "reacted badly" to Leiter's decision to repost his prior arguments. But I've done nothing but demonstrate that Leiter's theory cannot possibly apply to those scientists who rule out certain types of explanations "by definition." A true example of a bad reaction would be Leiter's own ever-increasing belligerence when I demonstrated (in a series of posts) that he had been gullibly repeating propaganda from a far-right-wing news source. See here, here, and here. Now, for the main point. As I have already
stated at
length, there are numerous scientists who say that science
by definition cannot take the supernatural into account in any way or fashion. What exactly are they doing when they say "by definition"? Leiter never even tries to explain.
A few of many such examples:
- Robert Pennock, who says that "once supernatural processes are wedged in, [the theory] loses any chance of testability," and that one "may, of course, retain religious faith in a designer who transcends natural processes, but there is no way to dust for his fingerprints."
- Eugenie Scott, who says that "invoking omnipotent supernatural causes puts one smack out of the realm of science, protestations of the validity of 'theistic science' notwithstanding. . . . Whether a supernatural force does or does not act is thus outside of what science can tell us."
Elsewhere, she says, "Supernatural causes are ruled out for philosophical as well as practical reasons: science requires testing of explanations against the natural world, and testing requires that some variables be held constant. Supernatural forces by definition cannot be held constant, thus supernatural explanation is outside of what science can deal with."
- Barry Palevitz, who says, "Science has no basis for acknowledging the possible influence of God in evolution, no matter how small or hypothetical. It's not that science excludes God so much as it has no way of dealing with the concept. Since it cannot be approached by scientific principles and methods, the supernatural is automatically off limits as an explanation of the natural world. It's not a factor in the equation; it's not in the same ballpark. All science can go on is material evidence, which says that the supernatural is not necessary for explaining biological diversity."
- Or there is Tim Berra, who says that "the scientific method by definition cannot deal with the supernatural."
To quote from two previous posts that discuss the above statements:
So what do people mean when they tell us that science by definition excludes the supernatural? According to Leiter, they are doing nothing more than relying on what has worked in the past. But that can't be it. Even the strongest inductivists would never say, "Because all the swans I've seen are white, therefore all swans are white by definition." If someone says that all swans are white by definition, she has taken a philosophical position that goes far beyond the mere fact that she has seen a few white swans.
Indeed, these definitions of science make no reference whatsoever to the quality of the evidence for the supernatural. These writers do not say, "For now, science excludes the supernatural, but that is only because there isn't good enough evidence yet. As soon as anyone comes forward with evidence of the supernatural, science will happily consider it."
No, that is not what they say at all. Instead, they say that science by definition excludes the supernatural. This is a belief that has nothing to do with the quality or poorness of any evidence that might exist. Whether one calls it "prior" or "a priori" or whatever is a semantic issue. What matters is that these writers have made a philosophical decision about how "science" should be defined, and about how to proceed henceforth in all future questions or experiments.
That is why there are two responses that are always made in the debate over Intelligent Design: 1) ID has no good evidence. 2) No matter what the evidence, ID relies on the supernatural, and as such cannot conceivably be scientific, period. Needless to say, these two rationales are not identical; the first relies on the quality of the evidence while the second does not; and I've seen the second far too often to be fooled by the odd assertion that it doesn't really exist.
And to quote from
another response:
[M]any scientists say that science "by definition" excludes any discussion of the supernatural. Just so there is no confusion, deliberate or otherwise, I'll say that this may be the best or most workable definition of science.
But if people say that one thing "by definition" excludes another, they are not merely arguing from their own experience, as Leiter attempted to claim. (Recall that Leiter had said that the definition of science is determined only by experience and evidence, i.e., what has worked before.) Experiences don't come pre-packaged into defined subjects. No collection of facts or experiences could enable someone to say "This discipline by definition includes this and excludes that." No: a discipline's definition is something that we human observers impose upon the world as a means of interpreting future experiences.
An analogy: Jack says, "In my experience as an archaeologist, I have never seen evidence that aliens ever visited this planet and caused any of the curious formations that we occasionally find. I therefore find it is best to assume for now that aliens don't exist, although I'll be interested to consider any hard evidence, if any ever turns up." Jill says, "Archaeology as a discipline by definition excludes any discussion of aliens."
It is not that Jill has offered a bad definition of "archaeology." That's not the point at all. She might have given the most workable definition available. Other archaeologists may cheer her on by saying, "Yes indeed, our discipline is not equipped to deal with the concept of aliens, much less the cranks and charlatans who would invade our territory if we let the gates open to that sort of explanation."
Still, is it not obvious that Jill has said something quite different from Jack? By thus defining her discipline, she has announced where archaeology is allowed to go in the future, and what sorts of evidence will be considered within its bounds.
Leiter never even attempted to answer this point, and he still doesn't.
In short, when scientists say that science
by definition excludes the supernatural, they are propounding exactly what Leiter himself labels an "a priori" belief, i.e., "a dogma immune from and indifferent to the empirical evidence." If science "by definition" excludes the supernatural, then it wouldn't matter if (in theory) any amount of high-quality evidence for the supernatural ever turned up, because science would have already "by definition" excluded such explanations.
Put it this way: If I say that "trigonometry by definition does not incorporate the study of Baroque music," it would make no difference to ask, "But what about a really good piece of Baroque music? Something by Bach?" No: That's just not the sort of thing that trigonometry is about.
Same with science, at least in the views of many scientists and commentators. Even if someone managed to produce absolutely unassailable evidence of a miracle or supernatural event, there would be many scientists who would say, "It doesn't matter how much evidence there is in favor of this event, it's just not the sort of thing that science can study." Even if the evidence indisputably "worked" for this one event, they would still view the event as non-repeatable, non-testable, outside the domain of science -- in other words, as "automatically off-limits."
TO REPEAT, this is probably a useful belief for scientists to have. But it's simply incorrect to claim or imply that there's no such belief.
ORIGINAL POST:
Brian Leiter
says, "VanDyke invokes another non-philosopher blogger as 'authority,' though this individual appears to be equally confused on this subject." The unnamed blogger is me, and the subject is whether scientists' devotion to methodological naturalism is "a priori." Needless to say, it is ironic to be called "confused" by someone who is either unable or unwilling to recognize that people might use the term "a priori" in more than one sense, and that at least one sense might be accurate.
Scientists often say as follows:
"Other scientists have seen that methodological naturalism has worked in the past; therefore I will approach any new problem with a strict insistence that
only naturalistic solutions will be considered, because I have decided that only naturalistic solutions count as 'science.'"
Leiter focuses on the first part of that sentence, and accordingly insists that methodological naturalism was not
collectively chosen "a priori" in the Kantian sense. That's all fine and well, but it says nothing about whether an
individual scientist
today approachs new problems having ruled out a particular type of solution without regard for its truth. In
that sense, the commitment to methodological naturalism is "a priori," because it comes prior to an individual scientist's investigation of any actual new problem or question.
What’s more, scientists
often define "science"
completely without regard for what has worked (or not) in the past, as if it were a matter of metaphysical impossibility (rather than contingent factual inquiry) that science could be defined otherwise. In other words, one can find countless examples where scientists say something akin to the sentence above
without the first clause. Why their approach doesn’t deserve to be called “a priori” in some sense is beyond me.
On a similar note, Mr. Myers
says:
We aren't saying that that couldn't have happened at all; maybe it did. Maybe alien tourists visiting the Earth 4 billion years ago decided to dump the holding tank in their Space Winnebago into one of our ponds, and that's how life started. Or maybe it's true that an invisible pink unicorn created the whole universe last Thursday, complete with an appearance of age and a collection of false memories in the minds of all of its inhabitants. We do not reject those ideas because of an a priori belief that they are false. They are rejected because we have acquired an a posteriori appreciation of the value of evidence. Evidence really seems to help us understand a lot of things, and has been a useful springboard for further work.
He then spends the rest of his post claiming that there is no evidence for Intelligent Design. That is fine, but again it is irrelevant. I never claimed that there is any evidence whatsoever for ID. What I said was that
even if there was such evidence, many or most scientists would rule out such evidence from the get-go, because they have adopted a philosophy that such explanations don't count as "science."
On this question, it sounds as if Mr. Myers is admirably open-minded, willing to follow the evidence wherever it leads, even if it turns out that everything is due to an invisible pink unicorn.
But most scientists don't share his open-mindedness. That's why they compose definitions of "science" that utterly rule out any possibility of the supernatural from the start (whether one wants to call this "a priori" depends on one's definition of "a priori," as I've pointed out).
There is Robert Pennock, who
says that "once supernatural processes are wedged in, [the theory] loses any chance of testability," and that one "may, of course, retain religious faith in a designer who transcends natural processes, but there is no way to dust for his fingerprints." Then there is Eugenie Scott, who
tells us that "invoking omnipotent supernatural causes puts one smack out of the realm of science, protestations of the validity of 'theistic science' notwithstanding. . . . Whether a supernatural force does or does not act is thus outside of what science can tell us." Or Barry Palevitz, who
says, "Science has no basis for acknowledging the possible influence of God in evolution, no matter how small or hypothetical. It's not that science excludes God so much as it has no way of dealing with the concept. Since it cannot be approached by scientific principles and methods, the supernatural is automatically off limits as an explanation of the natural world. It's not a factor in the equation; it's not in the same ballpark. All science can go on is material evidence, which says that the supernatural is not necessary for explaining biological diversity." I could multiply the examples indefinitely, but you get the point.
In short, we might distinguish between several varieties of belief here:
1.
Scientists collectively and historically decided "a priori" to adopt methodological naturalism, without ever having seen any evidence as to how it works. This view is possible, and it seems to be what Leiter and Myers thought they were refuting.
2.
Individual scientists working today begin their analyses of any new problems by having defined "science" as excluding supernatural possibilities. Collectively and historically, they have adopted this method because it has worked before. In that sense, it is "a posteriori." But as to any new problem, supernatural solutions are ruled out from the start. In that sense, it is "a priori." While one can quibble over the definition of "a priori," even a generous interpretation leads to the conclusion that this is how most scientists behave, and I can't see why any sensible person would disagree.
3.
Individual scientists working today do not rule out any possibilities whatsoever. If there is evidence for the supernatural, so be it. There may not be any such evidence, but that is purely a contingent matter. Whatever the evidence shows is where we should go. This is the view that seems to be put forward by PZ Myers and Intelligent Design advocates, who definitely differ as to the quality of evidence for ID, but apparently not as to the question whether any such evidence should be considered in the first place. This view is not often claimed by scientists.