Catastrophism is doctrine that explains the differences in fossil forms encountered in successive stratigraphic levels as being the product of repeated cataclysmic occurrences and repeated new creations. This doctrine generally is associated with the great French naturalist Baron Georges Cuvier (1769-1832). One 20th-century expansion on Cuvier's views, in effect, a neocatastrophic school, attempts to explain geologic history as a sequence of rhythms or pulsations of mountain building, transgression and regression of the seas, and evolution and extinction of living organisms.

There have been dramatic changes in attitude towards catastrophism since 1980, stimulated by the hypothesis of Luis Alvarez and colleagues that high iridium concentrations found at the Cretaceous-Tertiary boundary throughout the world could be taken as evidence that the mass extinction episode at the end of the Cretaceous Period had been caused by the impact of a large asteroid. Alternatively, the iridium abundance anomaly might have been the result of extensive vulcanism, which is known to have occurred at this time, but this would also have to be regarded as a catastrophist mechanism, and could even be linked to an impact.

In the case of catastrophism, as applied to geology (the study of the Earth) or palaeontology (the study of fossils), there can be little doubt that, in the eyes of the scientific establishment for a century or more, it has seemed as defunct as any theory could be. Now, however, catastrophism is making a very real contribution to geology and evolutionary theory. A resurrection would seem to have taken place.

Rightly or wrongly, it has generally been thought that the catastrophists of the nineteenth century and earlier believed that God was directly involved in determining the history of the Earth. So, for example, American palaeontologist, Steven Stanley, claimed in 1987 that catastrophism was the outmoded belief that sudden, violent and widespread events caused by supernatural forces formed most of the rocks visible at the earth's surface.

It should go without saying that twentieth century catastrophism, often called neocatastrophism, is founded entirely in science, relying solely on natural forces for its explanations, but was eighteenth and nineteenth century catastrophism completely different? Was it so dominated by supernatural elements that any scientific content it may have claimed was without value? That was certainly the prevailing view for most of the present century. Catastrophists have been condemned for putting dogma before observational science, whereas their rivals, the gradualists (also called uniformitarians) have been praised for taking the opposite stance.

This view of scientific uniformitarianism and dogmatic catastrophism was, at best, over-simplistic, failing to take into account the range of beliefs and attitudes of individual uniformitarians and catastrophists in the late 18th and early 19th centuries. For many centuries, the Church had exercised almost complete control over academic communications in the western world, and everything was viewed within a spiritual context. For most of that time, it would have been heretical to deny the testimony of the Bible, as accepted by the Church, that the Earth was only a few thousand years old, and that there had been a major cataclysm, the Flood in the time of Noah. Today, we ridicule Archbishop Ussher, who in the middle of the seventeenth century calculated, from information given in the Bible, that the Earth was created in 4004 BC. For whatever reason, we ignore the fact that Ussher's chronology was supported, in very positive terms, by no less a scientist than Sir Isaac Newton. Similarly, when rightfully praising Newton for formulating the mathematical laws of gravity, we turn a blind eye to the fact that he thought the gravitational forces themselves required a supernatural rather than a physical explanation.