As a historical figure, Lamarck proves a rather difficult subject. His writings give us few explicit leads to his intellectual debts; nor do they present his theories as the outcome of any sustained course of observations or experimental research; and, what is equally frustrating, it is hard to see how his personal development as a scientific theorist was affected by the dramatic political and social upheavals of the period, in which he took an active and lively interest. And so, with his importance for later writers much clearer than his relationship to those of his own and earlier ages, historians have repeatedly interpreted his works as prophetic of doctrines developed more fully by subsequent generations. No less surprisingly, this facile tactic has provoked a reaction; we have been offered Lamarck as a Stoic, a romantic, harking back to Heraclitus.

Heat is the fundamental mechanism in the theory of the earth proposed by James Hutton in 1785. According to Hutton, heat is responsible for the liquefaction of loose debris collected on the ocean floor. Consolidation follows and the newly formed land is raised above the sea by the agency of heat. The expansive nature of heat that causes this elevation of land also accounts for the creation of veins and dykes through the injection of fluid matter into openings in the earth. The activity of heat is intermittent; there are times when it is active, but at other times it is dormant. In another paper I argued that Hutton's concept of this geological heat was an application of his theory of matter in which heat is an immaterial, universally operating force acting in opposition to forces of attraction. This concept of heat was quite different from the popular late eighteenth-century belief that heat was a material substance called caloric. The critics of Hutton repeatedly tried to interpret his heat as if it were caloric. Failing in this they found Hutton a confusion of idle speculation on heat and without theoretical basis. Further, since fire was a major source of caloric and since the already established geological tradition of Vulcanism called for fires within the earth, it was natural that these critics thought of Hutton's theory as being necessarily based on the presence of internal fires and questioned how such fires could exist, disregarding the fact that Hutton rarely mentioned fires and even disclaimed the necessity of fires in the production of heat. The criticisms concerning heat fall into several major groups of which the source of heat in only one. The others include the formation of the whinstone of Scotland and the crystallization of rock in general, the expansive role of heat, the intermittent activity of heat, and the temperature of the earth. Of these the formation of particular kinds of rocks was submitted to experimenal test by Sir James Hall, whose investigations were especially concerned with the effects of the rate of cooling on crystallization and the effects of pressure on the formation of rock. Much of the discussion of Hall's work centred on the experiments, and the theoretical problem about the nature of heat was obscured as a result. It is in the commentary on the other problems noted above that the true situation becomes clear. For this reason a study of these problems is more revealing and constitutes the following.

Proclaiming Louis Pasteur as the “Founder of Stereochemistry”, the distinguished Scottish chemist, Crum Brown, addressing a late nineteenth-century audience of Edinburgh savants, drew attention—as Pasteur had incessantly done—to the intimate relationship between living organisms and the optical activity of compounds sustaining them. It seemed to Crum Brown “that we must go very much further down in the scale of animate existence than Buridan's ass, before we come to a being incapable of giving practical expression to a distinct preference for one of two objects differing only in being one to the right and the other to the left”. Crum Brown's lecture must have been entertaining, but it was also motivated by a serious desire to do justice to a particular assertion of Pasteur—an assertion which had, moreover, been misunderstood and dismissed by no less a chemical genius than Wilhelm Ostwald. Writing at a time when the majority of his colleagues were stressing the resemblances between inorganic and organic compounds, Pasteur had insisted that he “could not point out the existence of any more profound distinction between the products formed under the influence of life and all others” than that “artificial products have … no molecular asymmetry”. Pasteur was obliged to concede that the chemist might produce enantiomorphic pairs of isomers, but without resorting to a manual separation of crystals he was powerless to imitate Nature's performance, powerless to fabricate by chemical means a separate optical isomer, divorced from its partner. Now it was not only Crum Brown who felt that chemists had brushed aside this proposition of Pasteur. In his 1898 Presidential Address to the chemical section of the British Association, Professor F. R. Japp also complained that the possible vitalistic implications of Pasteur's distinction between natural and artificial products had been misapprehended or tacitly ignored.