Martin Rudwick's The Great Devonian Controversy is a monumental achievement and a classic in the philosophy and history of science. As a case study of one of the watershed moments in the history of geology, it is not only great history, but it is also a test case for theories about the nature of scientific knowledge. It is also well written, engaging, and fascinating as a narrative and a detective story, based on a great mass of material, including letters sometimes written on a daily basis between the principals of the dispute.
The story centers on arguments among the members of the British "Geological Society," based in London, in roughly the last half of the 1830's, over the mapping and interpretation of the geological strata of the county of Devonshire. While Roderick Murchison and Adam Sedgwick mapped the strata in Wales, establishing the classic Silurian and Cambrian systems (1835), respectively, their colleague Henry Thomas De la Beche was engaged in similar mapping in Devonshire. Everyone assumed that the rocks in Devonshire were approximately the same age as those in Wales. However, De la Beche found that the coal deposits already known to be in Devonshire were an integral part of the surrounding rock. This posed a problem because there was no coal, and not even any obvious plant life, in the older strata in Wales, the other coal deposits in Britain were in much younger rock (the "Carboniferous"), Murchison in particular did not believe that plants or coal existed at all in the earlier periods, and De la Beche himself was surprised when an examination of the Devon coal plants showed them to be all but identical to Carboniferous plants.
When De la Beche announced his results in 1834, Murchison leapt to the attack, even though he had never examined the strata in Devonshire himself. This deeply offended De la Beche, and others, who did not believe that the validity of field work should be questioned just for a priori and theoretical reasons. The Geological Society had been founded in the hope of avoiding the grand cosmological theories that had fruitlessly dominated much of earlier geology. As De la Beche himself said:
Let us hope that the day is past when preconceived opinions are to be set up, as good as arguments, against facts; because if they are, let that fact at least be clearly understood, and let us be consistent, and no longer boast of our adherence to the Baconian philosophy. [pp.105-6]
Although Murchison's complaint had originally been a priori, the tide soon turned as he and Sedgwick both examined Devonshire themselves in 1836. De la Beche had made a mapping error and it turned out that the coal deposits were at the top of the Devonshire strata rather than in the middle. This meant that the coal could simply be sitting unconformably (i.e. with a stratigraphic gap or "unconformity") upon the much older rock. For a brief period, this threatened to actually discredit De la Beche as a competent geologist. On the other hand, the problems with Murchison's case did not go away: De la Beche staunchly insisted that there was no unconformity between the coal strata and the older rock. To their discomfit, Murchison and Sedgwick could not actually identify the unconformity they assumed must be there, and soon Sedgwick had to admit, at least to himself, that there wasn't one.
With no unconformity, then either the coal must be very old, which was hard to imagine because of the fossils, or the underlying rock must be much younger, which was hard to imagine because it was so unlike the rock that lay under the coal elsewhere in Britain, mostly what was called the "Old Red Sandstone." What was worse, plants began to be found in the underlying strata themselves, which was mainly a problem just for Murchison, since most others were willing to accept that the absence of plant fossils in the Cambrian and Silurian rocks was a local accident. Murchison didn't want his "Silurian System" to be a local accident, but a universal type.
As a case study for the philosophy of science, this is an illuminating situation. After Thomas Kuhn's Structure of Scientific Revolutions, and its spinoffs in "deconstruction" and "post-modernism," a dominant view in many circles, at least outside of science itself, is that the "truth" of scientific theories is not determined by evidence or empirical data but by social "power" relationships. On that view, a theory is always able to protect itself by interpreting away any evidence against it. "Evidence" is so "theory-laden" that scientists will pretty much see what they want to see, and no empirical datum can simply falsify a theory in the straightforward logical way described by Karl Popper. In these terms, theories may push each other around, but there cannot be a situation where some "objective" evidence simply knocks out any or all of the available theories.
Kuhn's critique contains a considerable element of truth, since people, scientists included, often do just see what they want to see, and it is possible to explain away falsifying evidence. On the other hand, anomalies are often recognized that are inconvenient to a theory, and most scientists are now aware that if the theory cannot ultimately accommodate them, then a new theory will be necessary. And then there is the Great Devonian Controversy. Once all the major geologists recognized that there was no unconformity in the sequence, and that there were plants in the lower strata, there simply was no existing theory that could accommodate the facts. Thus, we had a situation that, in Kuhnian terms, was impossible. The evidence could not be interpreted to sustain any existing theoretical views.
The situation was sometimes discussed by participants in what sound like modern terms. Thus, John Phillips, professor of geology at King's College, in London, wrote to De la Beche that his discovery of certain plant fossils, "is a fact to be introduced into the induction, not an anomaly to be frightened at" [p. 223]. Here "anomaly" would mean just what it means now: Some fact inconsistent with a received or desired theory. As "Baconians," both Phillips and De la Beche think that the appropriate theories will be produced by "induction" from a sufficient catalogue of facts. Neither Kuhn nor Popper could agree with that old "Baconian" view of theories, but Kuhn and deconstructionists cannot allow that an anomaly all by itself could potentially falsify a theory, rather than vice versa. But in the Devonian Controversy, the anomalies overthrew all the theories.
In 1839, the solution was hit upon by Murchison, that the conformable sequence of strata in Devonshire was contemporaneous, at the top, with the Carboniferous but, lower down, not with anything Cambrian or Silurian, but with the Old Red Sandstone found elsewhere in Britain. This was now to be dignified as the "Devonian System." To propose this solution, Murchison had to give up his cherished theory that the fossil assemblages in contemporaneous formations should be identical. This had been dismissed as unlikely by De la Beche and most other geologists, for reasons of probable ecological and climatic variation. Now Murchison had to agree with them. As Rudwick says:
Now Murchison was being forced by the logic of his own interpretation to incorporate his opponent's suggestion, and thereby to abandon a central component of the rhetoric that had distinguished their positions hitherto. If the older strata of Devon were equivalent to the Old Red Sandstone, much that had been anomalous would in Murchison's view be resolved. But this could only be achieved at the cost of abandoning the full rigor of his insistence on fossil evidence, and of conceding the validity of his opponent's emphasis on the localized character of formations and their fossils. [p. 278]
Murchison's concern for the fossils is what drove his disagreement all along, at first even for a priori reasons. By finally accepting part of De la Beche's argument, Murchison could imagine a new theory that finally would pretty much fit all the facts. That is how scientific progress frequently occurs. The process, indeed, was not "theory free," but then it could no more be so in terms of Popper's philosophy of science than of Kuhn's. Indeed, Stephen Jay Gould has variously chronicled how false theories can actually be more productive to the progress of science than more sensible ones (cf. Gould's Time's Arrow, Time's Cycle), just because they can help throw certain kinds of evidence into a different light. But "a different light" does not imply the kind of open ended interpretability implied by deconstruction.
The theory about a "Devonian System" proposed by Murchison was eventually secured in the agreement of all significant geologists, though at least one participant continued to claim that he had actually found the elusive unconformity in Devonshire. Today the Devonian Period of the Paleozoic (a term coined by Sedgwick) Era, is an unproblematic part of the geological time scale.
Rudwick ends his book with a description of the social and logical dynamics of the Devonian Controversy. The lessons of the book thus do not go unexplained. Rudwick might as well have examined the sociology and logic of a situation where studies such as his go ignored by theorists who see only power, not evidence, and nothing but "social construction," not truth. But this is explained easily enough: For those who have no love or interest for science, but who have some real political cause to promote, and some rent-seeking constituency in academia to further, the best way to handle inconvenient truths such as those examined by Rudwick (and Gould) is to ignore them. That is a final, simple, and effective method to interpret away evidence: Pretend it doesn't exist. This can be effective enough, indeed, through a ruthless and dishonest use of political power, in academia and elsewhere. The dishonesties may even be evident to all, but, as we have learned from the history of totalitarian regimes, even the most transparent irrationalities and absurdities can, for a time, be made acceptable by political terror.
That educational institutions should come to enforce certain kinds of orthodoxy is not surprising, not because of the non-existence of truth or evidence, but because of the existence of bureaucratic rent-seeking and self-promotion. The life of European universities once before became so moribund that modern philosophy and science could mostly only start outside of them. Now, after the "Gentlemanly Specialists" like Murchison have disappeared and been replaced by grant-seeking academic professionals, this process has come full circle, though now with the added twist that academics may justify the irrational and dishonest nature of their views, not by arguing that they are the truth, but by arguing that truth doesn't exist! Karl Marx, the father of the "power relations" theory of ideology, would have had no difficulty understanding the bureaucratic obscurantism and self-serving nature of such ideas: The bureaucratic class thereby pursues its own self-interest.
The Great Devonian Controversy shows us a period when institutional arrangements were in flux and part of the dynamic was the different situation of each of the principals: Sedgwick was a professor and cleric at Cambridge; Murchison was a private, well-to-do gentleman of leisure; and De la Beche, although independently wealthy at first, was ultimately dependent on government funding of an official Geological Survey. Others were impecunious amateurs on the spot who pursued their local geology as a hobby. There is no doubt that this kind of mix was much healthier than the post-World War II dominance of government funding and government control in education and science, which has opened the possibility of just the kind of political and totalitarian control that many participants today would actually prefer. The previous safety valves of considerable local control, and of the ability of private fortunes (Carnegie, Rockefeller, Ford, etc.) to independently finance education and research, has gradually been undermined, not just by the growth of participation by the federal government in the United States, but by unrelenting attacks on private capital and just such private fortunes, upon which the Democratic Party rode to seventy years of dominance.
Rudwick's thorough and honest study, although unlikely to be fashionable in politicized academic circles, will at least exist for the edification and enjoyment of all real historians, philosophers, and scientists hereafter.
Philosophy of Science