Mobilism Emile Argand coined the term "mobilism" to describe his approach to horizontal movement of the Earth's crust, what Wegener called "continental drift". Argand's argument was based on the principle of Occam's Razor. He was not deterred by the lack of a mechanism for the mobility of the crust. The paleontologist, von Ihering, stated the position of most mobilists, "It is not my job to worry about geophysical processes" (Wegener, 1929). Unlike most of his mobilist contemporaries, Argand was a tectonist, an expert on the structure of mountains. His diagram of the Himalayas shows clearly that he envisaged subduction of the Indian plate under the Asian plate.

Theory in Earth Science Plate tectonics was not the first revolutionary theory concerning the Earth. Two others preceded it:   • The theory that the Earth is a sphere or nearly so, a spheroid;   • The theory that the Earth and other planets revolve around the Sun. Earth as a Planet Both of these theories relied on Occam's Razor rather than knowledge physical processes. By 1600, Shakespeare was able to have King Lear say:

And thou all-shaking thunder Smite flat the thick rotundity o' the world! (Lear, Act III, Scene 2).

Shakespeare was confident that the common people who attended his plays already knew the world is round. Ferdinand Magellan had sailed round it from 1519 to 1522. However, no physical process was known that could form the Earth as a globe. No mechanism was known for the formation of the solar system either. Galileo was criticized because observations did not provide better support to his model of the solar system than to the Ptolemaic model. Galileo's model rested on an appeal to Occam's Razor: it was simpler than the Ptolemaic model (Kuhn, 1962). Copernicus supported his own theory of a heliocentric universe by saying that it was more elegant than the Ptolemaic model, in effect invoking Occam's Razor. Not until Kepler published his laws of planetary motion from 1605 to 1619 did philosophers become aware of the mechanism governing the solar system. Later, Edmund Halley (1656-1742) applied Newton's laws of motion to arrive at a precise formulation of the mechanism. Long before such a mechanism was developed, the new theories had revolutionized cosmology. The poet Donne (1572-1631) commented on the impact of the new theories of the solar system:

And new Philosophy calls all in doubt, The Element of fire is quite put out; The Sun is lost, and th'earth, and no mans wit Can well direct him where to looke for it. (An Anatomy of the World, 1611)

Donne was impressed enough with Kepler to visit him in Austria. Six years after visiting Galileo, who was under house arrest in Italy, John Milton published his famous appeal for freedom of expression, the Areopagetica (1644). The new philosophy had spread across Europe and was accepted before the mechanism was developed.

Mobilism and Occam's Razor Wegener's hypothesis of continental drift had two components. The first component was mobilism, taken to mean only that continents move, without implying a specific mechanism. The second component of Wegener's hypothesis includes "drift", a specific mode of movement, thus going beyond what Occam's Razor would admit. Wegener's notion that the continents "drift" was a major barrier to the acceptance of the theory. Continents do not drift. Plate tectonics accounts for displacement of the continents by conceiving the ocean floor as a "conveyor belt" that carries the continents away from mid-ocean ridges. Imagine a climber on the slopes of a volcano overlooking a river of lava, molten rock flowing down the slope of the volcano. The climber throws a dinner plate onto the surface of the flowing rock. The plate does not drift down the slope; the plate is carried down by the molten rock. The Earth's crust flows more slowly than lava, and as it flows the crust carries with it the plates that bear the continents. Perception and Cognition In 1963, Fred Vine and Drummond Matthews of Cambridge University linked the concept of the magnetism of the Earth's crust to the theory of sea floor spreading proposed by Harry Hess of Princeton. This was an important key to modern plate tectonics because this linkage provided what was needed to test the theories experimentally. Vine described the moment when he first considered the theory of continental drift in April 1955, at the age of 15.

...I opened a physical geography text, probably for the first time, for as I recall, on the first page of the first chapter, there was a diagram illustrating the approximate fit of the Atlantic coastlines of South America and Africa. In the text, it stated that although it had been suggested on the basis of this fit that these continents were once part of supercontinent that subsequently split and drifted apart to form the South Altantic Ocean, geologists had no idea whether or not there was any truth in this hypothesis. I was struck at once by the boldness of the idea that seemingly stable continents might have drifted across the face of the earth in the past, and by the fact that we did not know whether or not this had occurred. It seemed to me that one could hardly conduct any meaningful study of the history of the earth until one had resolved this issue. Surely there must be some way of proving or disproving the concept of continental drift" (Vine, 2001).

Fred Vine looked at the same map that others had looked at. But he saw something that most others did not see: two hypotheses that were worthy of consideration. The image to the right above illustrates the point. Most people can see both the pedestal and the faces. The linked pages explore the idea that simple alternative realities can be visualized by almost everybody, but some are so complex that most people can see only one of the alternatives.

Training and Cognition During the 1960s geophysicists discovered what many geologists and geographers already knew: that the continents had once formed a surpercontinent that had fragmented, the parts having moved thousands of kilometers to reach their present positions. The earth-science community accepted the plate-tectonic view with little resistance because the evidence was conclusive. But was it really necessary to know the geophysical processes before accepting mobilism as a fact? The mechanisms and timing proposed by Wegener were not reasonable. Nevertheless, mobilism provided the simplest explanation of the observations. What if technology had developed faster than theory? What if the movement of the Earth's plates had been measured before Hess, Wilson, Vine, and Matthews had developed a mechanism to explain mobilism? What if the measured rates of plate movement allowed backtracking of present continents to the super-continent? This scenario would have presented the scientific community with the fact of mobilism without a mechanism. This is precisely what Argand, Du Toit, and the paleontologists claimed they had done by putting together a jigsaw puzzle using rock types, geological strata and fossils. Why was Drift Rejected? What needs to be explained is why continental drift was actively suppressed as a direction for research. At Harvard in the 1930s, continental drift was discussed only "on the back stairs". Steven Jay Gould said that in the 1950s at Columbia University, advocates of drift were publicly ridiculed (Oreskes, 1999). I recall a 1958 lecture in physical geography at the University of Western Ontario in which the lecturer set out the theory of continental drift. The lecturer, who was British, warned that no student who publicly supported continental drift could pursue an academic career in North America. I had seen a map similar to the one Fred Vine had seen, probably Du Toit's map. I was convinced by the geological arguments, but never discussed my views with anyone. In my opinion, the causes for rejection of mobilism lie both inside and outside the scientific disciplines classed as earth-science. This subject goes beyond the scope of this study and can only be touched on. Thomas Kuhn and Naomi Oreskes explored philosophical and scientific aspects of rejection, but the socio-political and psycho-social aspects of rejection have not been explored. In passing, Oreskes (1999) mentioned Schuchert's religious beliefs and the trial of Scopes for teaching evolution. Oreskes (2001) has also pointed out that only three institutions were responsible for the modern view of plate tectonics: Cambridge, Columbia and Princeton Universities and the Scripps Institution, with secondary input from professors at Canadian universities. These institutions enjoyed independence from political influence, both private and public. "It was downright un-American to be 'soft' on drift even as late as 1960" (Dott and Prothero, 1994). In the United States, the period from 1915 to 1940 was noted for its isolationism. From the 1920s until the 1960s, censorship of the arts was pervasive. Soon after the Second World War until after the Vietnam War, congressional committees, state legislatures and the Federal Bureau of Investigation monitored and harassed dissenters, including educators and media workers. Concern for academic freedom was not entirely extinguished by these efforts—in defense of academic freedom, professors could sometimes be heard muttering under their breath. In the context of social attitudes towards dissent, it does not seem strange that continental drift was suppressed. The socio-political and psycho-social aspects of scientific research are increasingly recognized, but historians of science have not yet examined rejection of continental drift from this point of view.

Return to Emile Argand Menu The URL of this site is [http://www.geoscience-environment.com]