In a previous post I suggested that sometimes theists and "naturalists" may, in the heat of their disputes, confuse the issue of "methodological naturalism." Anti-theistic philosophers and scientists share with theists a tendency to fixate on their differences over teleology, "supernatural" intelligence or design in nature and may more or less often drag this issue into disputes over "methodological naturalism." In fact there is no necessary connection between "methodological naturalism" and any position on the existence of design in nature, for example. "Methodological naturalism" is short-hand for insisting that scientific explanation confine itself to entities, processes, and events that can be detected by human beings, whether by direct sense experience or the use of instruments.
I think it is possible that some of the folks with whom I've disputed over this matter made this confusion. For that reason I plan to abandon the term "methodological naturalism" for the duration of this series of posts and talk about "detectability" and scientific method.
In her article on methodological naturalism Barbara Forrest quotes Arthur Strahler to the effect that introducing a single "supernatural" -- i.e, undetectable -- cause anywhere in a chain of causes making up a scientific explanation invalidates the entire explanation. Is this single invocation of an undetectable cause really so devastating? I think Strahler overstates the case, but qualified properly it still raises a legitimate issue.
Let's say, for example, I am sitting down to eat a stack of blueberry pancakes for breakfast and I suddenly have an overwhelming sense of deja vu. In my mind I am carried back to a memory of breakfast at a summer camp. I was at summer camp last year, but the camp in my memory is not the same as the one I actually attended. In fact, the location and the people sitting next to me don't resemble those at any summer camp I can remember attending. Joe psychologist explains to me that the smell and look of the pancakes triggered associations in my mind. The unrecognized location and visitors come to me by way of reincarnation. In a previous life I attended that very summer camp and sat with those very people for a breakfast of blueberry pancakes.
Strictly speaking, the event of reincarnation is unobservable. Sure, I can detect one of its supposed effects, the apparent memory of people and a place I otherwise don't recall, but the event itself is beyond reach. Nevertheless, for argument's sake let's say Joe psychologist is right. Furthermore, let's say that my experiences all conform to his diagnosis. I have repeated, striking experiences of deja vu, vivid dreams or nightmares, and always they include things that I have no memory of otherwise. Furthermore, let's say that all unrecognized details of these experiences can be traced to things experienced by the person I supposedly once was.
I can invoke several other undetectable causes to account for all the same phenomena, such as the presence of a demon who stole all these experiences from the other person and is planting them in my mind, or the existence of a post-mortem psychological memory "field" that radiates from the deceased person to another individual who can receive the memories on that "frequency." To the extent that these and other possible undetectable causes can account for all my experiences, past, present, and future, it doesn't really matter which one is correct. In fact, any and none of them could be correct, which means that Joe psychologist's explanation really amounts to "I don't know." This is one way Strahler may be thinking that invoking an undetectable cause invalidates scientific explanation. It amounts to an admission of ignorance.
I've already hinted at a qualification to Strahler's argument. Even undetectable causes can generate specific predictions about future observable events. Assuming the predictions following from various undetectable causes differ, one can falsify one or more of them if predictions fail. In this case the invocation of a specific undetectable cause is at least an implicit rejection of its undetectable competitors.
On the other hand, Strahler is on to something genuinely pernicious about invoking undetectable causes. Now that I have become convinced that Joe Psychologist is right, I am no longer driven to figure out where these apparent memories came from. I ascribe them all to my past life. With my critical faculties lulled to sleep I miss the clues, subtle or not, leading to a simple explanation that does not invoke an undetectable cause. To this someone will say, "Hey, the problem with reincarnation is not that it is undetectable, but that it is wrong!"
It certainly is wrong. Strahler may be drawing from historical experience here. Humans have often resorted to undetectable causes to explain the world, and in most cases their explanations were just plain wrong. But the invocation of the undetectable cause, wrapped in religious language and delivered with divine authority, became an obligation. To question it became a sin.
The appeal to an undetectable cause often discourages scientific research at precisely the point we would otherwise expect it to intensify. It is routine for scientists to encounter anomalies in their data, focus research on the anomalous situation, uncover new data, and use it to craft theories that resolve the anomaly. Reincarnation may explain my apparent memories, but further research may uncover more mundane causes and obviate the need to invoke reincarnation. This has happened often enough in the past, as Forrest points out in her articles. And it is this historical experience that grounds statements like those of Lewontin. The "a priori" refusal to allow undetectable causes in scientific explanation is really a lesson learned. Religions make many claims about undetectable causes for what appear to be anomalous events in the world but on further investigation it turns out that detectable causes fully account for them.
Does this mean that a scientist who happens to be a believer should pursue research that could lead to the falsification of his beliefs? Damn right! I will work this out in detail when I get back to my series on Eve as a scientist in the garden of Eden.