The issue of MN/PN came up in my class last week and in comments. I don’t really have time to adequately deal with the questions at the moment, but I do want to link to these two posts by Larry Moran and John Pieret on a talk given by Maarten Boudry, the abstract of which I give below:
In recent rounds of debate between evolutionists and supporters of Intelligent Design, the principle of methodological naturalism (MN) has been an important battleground. Creationists and intelligent design proponents have previously claimed that the commitment of evolutionists to naturalism and materialism constitutes a philosophical prejudice on their side, because it rules out any kind of supernatural causes by fiat. In response to these charges, some philosophers and scientists have argued that science is only committed to something they call methodological naturalism: Science does not deal with supernatural causes and explanations, but that does not mean that the latter do not exist. However, there has been some philosophical discussion about the correct understanding of MN. The principle of MN is often conceived of as an intrinsic and self-imposed limitation of science, as something that is part and parcel of the scientific enterprise by definition. According to this view (Intrinsic MN or IMN) – which is defended by people like Eugenie Scott, Michael Ruse and Robert Pennock and has been adopted in the ruling of Judge John E. Jones III in the Kitzmiller vs. Dover case – science is simply not equipped to deal with the supernatural and therefore has no authority on the issue. It is clear that this depiction of science and MN offers some perspectives for reconciling science and religion. Not surprisingly, IMN is often embraced by those sympathetic to religion, or by those who wish to alleviate the sometimes heated opposition between the two.
However, we will argue that this view of MN does not offer a sound rationale for the rejection of supernatural explanations. Alternatively, we will defend MN as a provisory and empirically grounded commitment of scientists to naturalistic causes and explanations, which is in principle revocable by future scientific findings (Qualified MN or QMN). In this view, MN is justified as a methodological guideline by virtue of the dividends of naturalistic explanation and the consistent failure of supernatural explanations in the history of science.
We will discuss and reject four arguments in favour of IMN: the argument from the definition of science, the argument from lawful regularity, the science stopper argument, and the argument from procedural necessity. Moreover, we will argue that defining the supernatural out of science is a counterproductive strategy against ID creationism, and, for that matter, against any theory involving supernatural explanations. More specifically, IMN has been eagerly exploited by proponents of ID to bolster their false claims about the philosophical and metaphysical prejudices of evolutionists. As ID proponent Philip Johnson rhetorically noted, if science is about following the evidence wherever it leads, why should scientists exclude a priori the possibility of discovering evidence for the supernatural? Therefore, IMN is actually grist to the ID mill.
We conclude that IMN is philosophically artificial and that its attempt to reconcile science and religion is ill-conceived. QMN, alas, does not provide any such ready reconciliation either, but it does offer a sound rationale for the rejection of supernatural designers in modern science.