philosophy and geology Philosophy and the sciences interact in several ways. The metaphysical foundations of whole ways of thinking are affected by and affect the conceptual frameworks of sciences that at different times play a salient role in their time. But there are also mutual influences between philosophy and scientific method to be discerned in the way scientific research in particular fields is conducted. Both these kinds of mutual influence can be seen in the history and practice of the science of geology.
Metaphysics
The thought of any epoch is imbued with certain taken-for-granted principles that are sometimes brought to light in controversies that seem to be on the boundaries between science proper and broad metaphysical abstractions. The deep foundational role of conceptions of time in the world-views of post-Renaissance civilization has been intimately interwoven with geologists' revelations and debates concerning the history of the Earth and the processes that have led to its current state. We can hardly imagine the Darwinian conception of organic evolution in separation from Hutton's expansion of the finite temporality into at least the possibility of immense ages. The two great debates in geology between neptunists or Wernerians (who held that the present state of the Earth is the result of a flood) and the vulcanists, for instance Hutton (who held that the present state of the Earth can be understood only by reference to the action of great heat), and between catastrophists (changes are discontinuous and violent) and uniformitarians, for example Lyell (changes are gradual), were also debates about time. The neptunists and catastrophists were generally finitists, and their opponents were in favour of an open geological time. Cutting across these debates were differences of commitment to an Earth created by natural processes and one brought into being by God. These debates were of far-reaching philosophical import in that they brought novel and disturbing metaphysical issues to the attention of the educated public in a specially dramatic way.
The metaphysics of the early period of scientific geology was part of a larger shift away from a human-centred world-view. The very possibility of volcanists in debate with neptunists, and catastrophists with uniformitarians, depends on the adoption of time-frames very different from those derived from the human life-span. Much the same shift from a human foundation for science occurred in the late eighteenth century in other branches of science; for example, in the creation of temperature scales, such as the Celsius scale, in which the temperature of the human body played no role.
Methodology: the boundaries of the ‘scientific’
But what of the methodology of geology as a science? As Rupke has shown, instancing the famous painting of Pegwell Bay by William Dyce as a turning-point, geological studies and landscape painting were closely interwoven. The transition from a representation of a portion of the Earth's surface for aesthetic reasons into an illustration of geological formations occurred around the 1830s. The insight that the state of the visible surface was in need of explanation called into play two different scientific procedures, each of which tried to explain the observed state of the Earth by reference to unobserved states and processes.
There was the question of explanations of the present by reference to past states of the Earth, in the situation that knowledge was needed of processes that had occurred at times when there were no human observers to make records even in principle. Whatever happened in the past was not directly observable in the present. But there were traces. By what inductive assumptions were inferences to the past to be made from the present, to reveal states of affairs which could then, without circularity, be cited in explanations of the very present from which they were themselves derived? How were geologists to justify their ‘readings of the rocks’? The status of fossils engendered philosophical debates, and the last-ditch claim of the creationists that they were put there to test our faith is not unheard even today.
From the point of view of scientific method we could look on the debates between vulcanists, neptunists, catastrophists, and uniformitarians as a long-running discussion as to the best inductive principle to adopt in trying to break the circle between the present as an ensemble of traces and the past as their sources. The advent of radioactivity as an inductive principle is technically novel but much in the tradition of geological inductions.
There was, however, another realm of unobserved phenomena about which hypotheses began to have a prime place in geological method. There was the question of structures within the contemporary Earth that are deep below the surface explaining the contours, rock formations, and so on that were directly observable. Philosophers of science generally refer to imagined structures playing this role as ‘models’. The creative imagination of geologists is demanded in the construction of models of subterranean processes and structures not currently directly observable. The logic of model-building is more complex than that engaged in the hypothetico-deductive method. Grounds for belief in the representational authenticity of models must be found before their acceptance is widespread. Geology offers one of the most interesting examples of a debate on the viability of a powerful model of a whole-Earth process, namely continental drift and its descendant, plate tectonics. The idea has a long history but its formulation early in the twentieth century by Wegener sparked an acrimonious debate. The arguments are illustrative not only of the logic of model-building but also of the recent insight that belief among scientists is as much a matter of social and psychological forces as it is the result of a cool assessment of evidence. On the one hand Wegener's hypothesis ran into scientific difficulties. As Hallam says, ‘the greatest stumbling block to acceptance of Wegener's hypothesis involved the nature of the underlying mechanism.’ Wegener's model needed another model, of the engine that drives the drift. On the other hand it provoked the ire of the conservatives that are found in every scientific field. Jeffreys declared it ‘unscientific’ because it was based on ‘qualitative data’. R. T. Chamberlin attacked not so much the theory as the upstart Wegener with ‘barely suppressed fury’.
Most sciences have their scandals, moments at which the defenders of an entrenched ‘mainstream’ turn on an innovator with some ferocity. Geology's moment has come and gone. Who now would reject what we now call ‘plate tectonics’? Geology touches philosophy both at the point at which our being as humans in a vast and open cosmos comes into question, and at the more mundane but no less vital point at which the disciplines of scientific method are to be defined.
R. Harré
Bibliography
Gillispie, C. C. (1951) Genesis and geology. Harvard University Press, Cambridge, Mass.
Hallam, A. (1973) A revolution in the Earth sciences: from continental drift to plate tectonics. Clarendon Press, Oxford.
Hutton, J. (1795) Theory of the Earth with proofs and illustrations. 2 vols. Edinburgh.
Lyell, Sir Charles (1830–3) Principles of geology. London.
Rupke, N. A. (1983) The great chain of history: William Buckland and the English school of geology. Clarendon Press, Oxford.
