Chemical Education Today
Commentary: Reviewer Comments
A Discussion of “Can Reaction Mechanisms Be Proven?” Peter A. Wade Department of Chemistry, Drexel University, Philadelphia, PA 19104;
[email protected] The aphorism that “Mechanisms cannot be proven, only disproven” is a cornerstone of modern science. However this aphorism has never stopped scientists from obtaining data to support a mechanism. Supporting data are an ingrained part of the scientific method as practiced. A mechanism that has a large body of supporting data is considered well-established and is provisionally treated as correct. In short, logic prevails in the current state of affairs. In my opinion, Buskirk and Baradaran have taken an extreme position in claiming that the aphorism requires us to accept that, “Only evidence that refutes or falsifies a mechanism is meaningful”. This has never been mainstream scientific practice. There is no conflict between the concept that “mechanisms cannot be proven” and the concept that with sufficient supporting data, mechanisms can be considered well-established and treated (always provisionally) as correct. Many well-established mechanisms have stood the test of time and will continue to do so. Others will likely need to be altered as new data become available. Alterations will continue despite—indeed because of—our ever more sophisticated tools and techniques. “Proving” a mechanism will remain elusive since all mechanisms are established on the basis of indirect evidence of one form or another. This is true whether or not there are direct spectroscopic observations of all suspected intermediates, since there is always the possibility others are
present or that one of those present is incorrectly placed in the overall scheme. Computational results, even those based on ab initio calculations, contain assumptions and are therefore subject to future refinement that just might substantially alter conclusions. It is unnecessary, even dangerous, to throw out the aphorism that “mechanisms cannot be proven, only disproven”. Which mechanisms are to be regarded as “proven”? Who will decide? Can this concept of “proven” be extended elsewhere in science? Let’s take an extreme example: there are undoubtedly those who would assert that creation science has “proven” the intelligent design theory of species selection. As in Karl Popper’s day, there are those who would abuse generally accepted alternatives to testability as precepts for studying scientific phenomena. Testability was defined by Popper as falsifiability. In conclusion, I take strong exception with Buskirk and Baradaran’s premise that “mechanisms can now be proven”. Perhaps this is mainly a semantic difference, since they have hedged this premise by saying, “It is true that mechanisms cannot be proven with philosophical certainty”. The current usage of “well-established” seems to equate to Buskirk and Baradaran’s suggested use of “proven”. However, it is my opinion that exchanging “proven” for “well-established” is a step backward in science. I plan to continue accepting mechanisms as well-established but not provable and doing chemistry rather than philosophy.
This article has been reformatted from its original appearance in the print Journal.
558
Journal of Chemical Education • Vol. 86 No. 5 May 2009 • www.JCE.DivCHED.org • © Division of Chemical Education
