To the editors:
Mike Leeder has provided an admirable introduction to the late-eighteenth-century Scottish savant James Hutton, who has been widely recognized as the founder of modern geology.1 What is missing from this overview of Hutton’s life and scientific achievements is reference to various controversies. These involve reactions during the early nineteenth century to his theory, recent debates concerning the importance of his role in the development of geology, and a critical look at his methodologies as they relate to current philosophies of geology.
There is no question as to Hutton’s continuing status as a prodigious figure in geology. He is accorded a prominent role in introductory textbooks and popular writings on the subject. As Leeder points out, Hutton gets credit for the discovery of what John McPhee has termed deep time.2 Hutton’s view of an Earth system, with cyclic operations driven by the internal heat of the planet, also seems to foreshadow current geological concepts of global tectonics. In A Brief History of Nearly Everything, Bill Bryson writes of Hutton: “[A]lmost singlehandedly, and quite brilliantly, he created the science of geology and transformed our understanding of the Earth.”3 In another popular work, The Man Who Found Time, Jack Repcheck claims that there were four key figures in the “freeing of science from the straightjacket of religious orthodoxy”: Nicolaus Copernicus, Galileo Galilei, Charles Darwin, and Hutton.4
The need for a founding scientific hero seems especially strong in geology, a science marked by tension between its deeply historical and its more causal and physical aspects. That tension was recognized early by the philosopher and historian of the inductive sciences William Whewell. Geology, according to Whewell, is palaetiological, literally a science of past causation, or a study of past causes.5 In other disciplines as well, including archaeology and ecology, the palaetiological sciences are receiving new interest from philosophers of science.6
The historical versus causal tension in geology has been addressed in modern histories that involve Hutton. Several of these claim that the causal aspects of Hutton’s grand theory diminished its influence on many of the geologists of his day.7 These aspects include the cyclic nature of Hutton’s so-called earth machine, its apparent eternal existence, and the linked, steady processes that characterize the cycles—all issues Leeder describes. Some modern historians also believe that past historians overemphasized Hutton’s role in the development of geology; they find equally, if not more, important influences from some of his contemporaries on the continent.
In the modern debate on the historical versus causal dichotomy, scholars have questioned whether geology’s focus on unique historical events makes it different from other physical sciences,8 or, alternatively, whether there is no real difference, according to the philosophies of logical empiricism or critical rationalism.9 An enthusiastic proponent of the latter position, Celâl Şengör, claims: “[T]here is no logical difference between the historical disciplines and natural sciences, and thus there is nothing unique about geological reasoning.”10
Hutton wrote extensively on epistemology, and Şengör refers to these writings to support his contention that Hutton’s theory of growth in scientific knowledge is similar to, if not identical with, the critical rationalism advocated by Karl Popper.11 In common with the logical positivism that it was intended to replace, Popper’s philosophy is based on the practices of physics, particularly inspired by the theoretical work of Albert Einstein. This physics-based viewpoint has implications for both divining the Earth’s natural history and for studying the history of geology as a science.12
Şengör argues against those historians who question Hutton’s role in the development of geology or disparage his reputation as the founder of modern geology. He believes they misunderstand Hutton’s influence on the natural philosophers of his day. Şengör has produced a researched and exceptionally detailed volume to support these views, entitled Revising the Revisions.13
During Hutton’s lifetime, a major controversy concerned his belief that over “deep time” the diverse features of Earth’s surface came about through “the effects of steady causes.” As Hutton expressed this concept,
Man … seeks to know how things have been, and what they are to be. It is with pleasure that he observes the order and regularity in the works of nature … and he is made happy from the appearance of wisdom and benevolence in the design … We should thus acquire some knowledge of the system according to which this world is ruled, both in its preservation and production … It must not be imagined that this undertaking is a thing unreasonable in its nature; or that it is a work necessarily beset with any unsurmountable difficulty; for, however imperfectly we may fulfil this end proposed, yet, so far as it is natural causes that are to be ascribed to the operations of former time, and so far as, from the present state of things, or knowledge of natural history, we have it in our power to reason from effect to cause, there are, in the constitution of the world, which we now examine, certain means to read the annals of a former earth.14
From this and other passages, it is clear that Hutton reasoned “from the present state of things” to study how “steady causes” operated with “order and regularity” over long periods of time, leaving such traces as to allow observers to “read the annals of a former earth.” In contrast, many of Hutton’s contemporaries held that changes in the past sometimes required processes with magnitudes and intensities much greater than what could be observed at present. Such processes were held to explain, for example, the extinction of certain animal species. These differences became even more apparent after Hutton’s theory was elaborated by John Playfair, with subsequent important modifications by Charles Lyell.15 The resulting controversy was highlighted by Whewell, who pitted what he termed to be uniformitarians, such as Hutton, Lyell, and followers, against catastrophists.16 There has since been much debate on both the meaning and the geological relevance of uniformitarianism.17 Elementary textbooks continue to teach that various forms of that doctrine are fundamental to geology.
Hutton freed natural scientists from the need to invoke catastrophes like the Noachian debacle to explain geological phenomena. He is, as well, often seen as a hero in the struggle to separate geology from the rigid temporal framework imposed on Earth history by biblical literalism. As Leeder points out, Hutton professed to being an ardent deist. He did not claim belief in a god tinkering with every aspect of reality, but rather in a beneficent force that created a long-enduring, possibly even eternal, world cycling for the benefit of humankind. But was this truly a deeply held motivation for the Huttonian theory, or was it a strategy to mollify purists of the Protestantism that prevailed in his world?
In comparing Hutton’s historical approach with that of Karl Marx,18 Şengör hypothesizes that Hutton may have really been an atheist, or at least an agnostic, so that his professed deism and invocations of design for the Earth were merely stances adopted to achieve acceptance in his own times. Other scholars, such as Martin Rudwick, disagree. In his own work on the history of geology, Rudwick aims to debunk the popular view of early Earth scientists as struggling to overthrow religious restrictions. But he observes that if Hutton did indeed place religious references in his writings despite his convictions to the contrary, it would be the equivalent of the practice of Russian scientists who employed Marxist language in their papers published during the Soviet period.19
Uniformitarianism aside, Hutton’s extended statement quoted above presents something critical to geological reasoning: the need to make logical inferences from effects to their causes. The late historian of geology David Oldroyd saw Hutton make such inferences in his observations at Siccar Point.20 Hutton observed effects—tilted marine strata unconformably overlain by relatively flat-lying continental beds—that resulted from the causal sequence of deposition in the sea, followed by heat-generated uplift, followed by erosion, followed by more deposition. Hutton reasoned from effect, q, to cause, p. These are combined in an argument of the form “If p then q; q therefore p.” Oldroyd notes that such reasoning is not deduction, and indeed that it constitutes a logical fallacy known as affirming the consequent. Even if with certainty the antecedent p will always lead to q, there is no logical basis for concluding that the finding of q will require p. The only proper logical argument is known as modus tollens, and it goes as follows: if p then q; not q; therefore not p.
One approach to dealing with what seems to be a logical fallacy in geological reasoning is to claim that this is not what Hutton, and all other geologists, are doing when they reason from effect to cause. Indeed, this is the approach of Şengör. He claims that Hutton is acting as a critical rationalist in the tradition of Popper, rejecting the inductive modes of inference in science and replacing them with a doctrine of falsifications through conjectures and refutations.
There is an alternative way of looking at this issue for geology, and it was pointed out in an underappreciated book Theorie der Geowissenschaft (Theory of Earth Science) by the geologist Wolf von Engelhardt and the philosopher Jörg Zimmermann.21 Following ideas from the pragmatist logician and geophysicist Charles Sanders Peirce, von Engelhardt and Zimmerman argue that geologists employ abductive reasoning, which is something that can be traced back to Aristotle.22 The goal of abductive inference is not absolute certainty from theoretical explanation, as produced in physics through deductive inference from true premises. Rather, abductive inference is focused on achieving a fruitful line of inquiry as part of an investigative approach focused on the detailed effects—in geology, the rocks, fossils, and structures that can be observed in the natural world.23
In a 1916 lecture, the logician and philosopher Alfred North Whitehead observed, “A science that hesitates to forget its founders is lost.”24 Whitehead was concerned about the tendency to invest too much authority in the founders of a particular science. In the introduction to his major work on process philosophy, he expressed admiration for the American pragmatists William James and John Dewey.25 As with Popper’s critical rationalism, pragmatism is antifoundational. For Whitehead, it is not the presumed foundations that matter to a science, but rather it is the continuing application of logic in moving science forward. But one must be careful to think through how the various logical principles are to be applied. In the pragmatist view, it is the effects of what follows logically from the consequences of scientific hypotheses that provide meaning and understanding. Moreover, the abductive mode of inference is essential to developing those hypotheses.
In this spirit, it is worth taking note of Whitehead’s proposal of anti-foundationalism in regard to history, which does not imply that history lacks value for scientific thought today. The history of science reveals much about the thinking, attitudes, controversies, and mistakes that involved earlier scientists. But a truly scientific attitude is fallibist; while scientists can temporarily take pride in discoveries that seem to work out, logical principles hold that scientists can never be absolutely sure of their truth. The process of science itself, much like Hutton’s theoretical Earth machine, may well have “no vestige of a beginning, no prospect of an end.”
Victor Baker
Mike Leeder replies:
Historians of science tend to focus on history and epistemology rather than on science. In my essay, I eschewed the non-scientific matters explored by Victor Baker in his letter. I did this by emphasizing that James Hutton’s Theory of the Earth is far more than a historical work, presenting as it does the first viable view of the outer planet as a cycling entity driven by internal heating—a de facto machine, designer-built for the purpose. Shorn of Hutton’s deism, his idea has become a Lazarus theory since the advent of plate tectonics and global biogeochemical cycling. It is an unparalleled achievement—a late-Enlightenment scientific theory resurrected in the nuclear age.
Briefly summarized, Hutton’s Theory comprises a brilliant deductive core statement—the cycling machine—supported by causal inference. Earth’s mountainous parts are produced by violent redistribution of internal heat and are reduced by subsequent erosion—a process repeated ad infinitum. Causal inference came courtesy of clinching evidence from field observations in Scotland, introduced in his revised scheme of 1794: the double discovery of examples of unconformities and the occurrence of once molten igneous intrusions in the Grampian Mountains. Hutton’s cycles were discrete, successive, and widely separated in time. They enabled a firm basis for the division of geological time into Primary and Secondary epochs. Those terms had already been in use, but now were more definitely defined. Hutton’s famous “no vestige … no prospect” quotation hence cunningly allowed for both previous, yet unrecognized, cycles as well as future ones.
What was it then about the causal aspects to Theory that, according to Baker’s cited authors, supposedly frightened off many geologists in the first half of the nineteenth century? My view is that it was because physics had to be called in for explanation; the cycles made by the Earth machine needed physical explanation of the most basic kind. Hutton’s close friendship with James Watt and a knowledge of his heat-driven steam engines and of contemporary blast furnaces must have provided a direct inspiration. Hutton realized that mountain building in opposition to gravity could only be the result of thermal processes. Elaboration of his conclusion would have to wait until Lord Rayleigh and others in the early twentieth century discovered convectional heating and Arthur Holmes in 1929 first applied it to Earth’s mantle.
It is no surprise that the lack of a viable causal mechanism troubled early geologists. It took both the mellifluous words of mediator John Playfair, in his Illustrations of the Huttonian Theory (1802), and a barrister’s confident reasoning, by Charles Lyell in his Principles of Geology (1830–32), to serve up even partly Hutton’s main menu of cyclic mountain building. All that was substantially left over was the palatable but dilute message of Lyell’s version of Huttonian uniformitarianism. The study of global tectonics began its long and difficult journey back into fashion only when Charles Darwin gathered compelling evidence for the periodic uplift of western South America and the Andes, which he published in the early 1840s.
