Vitalists hold that living organisms are fundamentally different from non-living entities because they contain some non-physical element or are governed by different principles than are inanimate things. In its simplest form, vitalism holds that living entities contain some fluid, or a distinctive ‘spirit’. In more sophisticated forms, the vital spirit becomes a substance infusing bodies and giving life to them; or vitalism becomes the view that there is a distinctive organization among living things. Vitalist positions can be traced back to antiquity. Aristotle’s explanations of biological phenomena are sometimes thought of as vitalistic, though this is problematic. In the third century bc, the Greek anatomist Galen held that vital spirits are necessary for life. Vitalism is best understood, however, in the context of the emergence of modern science during the sixteenth and seventeenth centuries. Mechanistic explanations of natural phenomena were extended to biological systems by Descartes and his successors. Descartes maintained that animals, and the human body, are ‘automata’, mechanical devices differing from artificial devices only in their degree of complexity. Vitalism developed as a contrast to this mechanistic view. Over the next three centuries, numerous figures opposed the extension of Cartesian mechanism to biology, arguing that matter could not explain movement, perception, development or life. Vitalism has fallen out of favour, though it had advocates even into the twentieth century. The most notable is Hans Driesch (1867–1941), an eminent embryologist, who explained the life of an organism in terms of the presence of an entelechy, a substantial entity controlling organic processes. Likewise, the French philosopher Henri Bergson (1874–1948) posited an élan vital to overcome the resistance of inert matter in the formation of living bodies.
The role of vitalism in physiology is exemplified in the work of the French anatomist Xavier Bichat (1771–1802). Bichat analysed living systems into parts, identifying twenty-one distinct kinds of tissue, and explaining the behaviour of organisms in terms of the properties of these tissues. He characterized the different tissues in terms of their ‘vital properties’, as forms of ‘sensibility’ and ‘contractility’. Bichat thought the sensibility and contractility of each tissue type constituted the limit to decomposing living matter into its parts. These vital properties preclude identifying life with any physical or chemical phenomenon because the behaviour of living tissues is irregular and contrary to forces exhibited by their inorganic constituents. Insofar as living matter maintains itself in the face of ordinary physical and chemical processes that would destroy it, Bichat thought it could not be explained in terms of those forces. He therefore allowed that there are additional fundamental forces in nature that are on a par with those Newton ascribed to all matter: ‘To create the universe God endowed matter with gravity, elasticity, affinity…and furthermore one portion received as its share sensibility and contractility’ (Bichat 1801, vol. 1: xxxvii). These are vital properties of living tissues.
The key to explaining the distinctive properties of living systems is showing how those properties stem from the constitution of the system. Bichat traced the properties of living systems back to their components; when this was done, the vital properties assigned to these components were opposed to their physical properties. François Magendie (1783–1855) provides a useful contrast. Many of Magendie’s experiments mirrored those of Bichat, but he interpreted them as revealing the different steps in a physiological process. Magendie’s (1809) avowed goal was to abolish the vital properties known as sensibility and contractility, and to ‘consider them as functions.’ Magendie rejected a mechanistic account of those functions, and acknowledged that many physiological phenomena remained beyond experimental reach, so that it was not possible to explain them in more basic physical terms. Because he acknowledged this distance between vital functions in living organisms and what it was possible to explain in physical terms at the time, Magendie was construed by many as a vitalist; if he is a vitalist at all, his vitalism is very different from that of Bichat.
Inspired by Lavoisier’s new analysis of combustion, and his demonstration with Laplace in 1780 that respiration in animals is ‘slow combustion’, chemists in the early nineteenth century hoped to explain many of the reactions found in living organisms. Organic compounds are apparently formed only in living organisms, and thus appear to be products of vital activity. The physiological chemists of the early nineteenth century set out to show, contrary to initial appearances, that these products are the results of chemical processes. Jacob Berzelius (1779–1848) argued that chemistry could account for all of the reactions occurring within living organisms, and that organic and inorganic processes differ only in complexity. ‘There is’, he said, ‘no special force exclusively the property of living matter which may be called a vital force’ (Berzelius, 1836).
A vitalistic view of the relationship of chemistry to physiology is found in Justus Liebig’s (1842) study of chemical reactions in plants and animals. In animals he was particularly interested in reactions which metabolize foodstuffs, separating the constituents needed for growth. Liebig offered detailed chemical analyses of the sequence of reactions, based upon chemical analysis of the foods taken in, the products absorbed, and the waste products released. Liebig saw a need for some form of regulation of these reactions, and posited a vital force controlling them. Chemical and vital processes operate in opposite ways, and consequently both sorts of process are necessary in order to understand metabolism. Liebig’s vital forces were not meant to undermine a mechanist programme; rather, they are forces comparable to other physical forces such as gravity and chemical affinity that are possessed by matter and would be exhibited under appropriate conditions. ‘There is nothing to prevent us from considering the vital force as a peculiar property, which is possessed by certain material bodies, and becomes sensible when their elementary particles are combined in a certain arrangement or form’ (Liebig 1842). Vital forces were invoked to explain phenomena which would otherwise lack an explanation.
Though Berzelius and Liebig were divided over what vital forces they would tolerate, they were united in the desire to explain activities in living organisms in chemical terms. They thought vital forces were necessary because some phenomena have no adequate chemical explanation. Their position is evident in the stance they took on fermentation: it is a chemical process and should be interpretable in chemical terms, whether it is occurring within living organisms or in the test tube. They viewed fermentation and putrefaction as the least challenging cases for chemists, since both processes are simply processes of decomposition and thus the result of simple chemical activity of the sort found in inorganic cases. With the development of better microscopes, Theodor Schwann (1810–82) observed in 1838 that single-celled organisms (yeasts) are involved in fermentation, setting the stage for a controversy that continued for the rest of the century. Schwann and Louis Pasteur (1822–95) argued that fermentation was an activity of whole living organisms and not reducible to ordinary chemistry. This seemed to be a vitalist position. Schwann, though, advanced a mechanistic theory of cell formation, claiming cells simply constitute special environments in which ordinary matter appears in different concentrations. This is not vitalistic. Pasteur, by contrast, fitted fermentation into a more general programme describing special reactions that only occur in living organisms. These are irreducibly vital phenomena. Pasteur demonstrated empirically in 1858 that fermentation only occurs when living cells are present and, further, that cells only carry out fermentation in the absence of oxygen, leading him to describe fermentation as ‘life without air’. Finding no support for claims such as those advanced by Berzelius, Liebig, Traube and other chemists that fermentation resulted from chemical agents or catalysts within cells, Pasteur concluded that fermentation was a ‘vital action’.
In addition to their apparent success in showing that fermentation only occurs in living cells, vitalists like Pasteur also appealed to their demonstration that living organisms always originate from living organisms and that there is no spontaneous generation. The idea of spontaneous generation was inspired in part by the observation of small organisms forming in putrefying matter. The controversy is rooted in the conflict between John Needham (1713–81) and Lazarro Spallanzani. Needham heated closed vessels of meat-broth, discovering that when cooled they still yielded micro-organisms. Spallanzani insisted on longer heating, and in his vessels no micro-organisms developed. In this context, Pasteur showed that heated organic matter remained sterile unless contaminated but that, if contaminated, the previously heated material sustained life. This supported the conclusion that new life-forms only emerge from existing ones and provided additional evidence for the vitalist claim that living organisms are inherently different from non-living entities.
Perhaps the greatest challenge for a mechanist, and the context in which vitalism retained its influence most strongly, was development. Beginning with an undifferentiated and singular egg, development results in an organism with a regular and differentiated structure. The problem is to explain how this regular differentiation is possible. Descartes defended an epigenetic view of embryological development; however, Descartes could not explain how a complex living organism could result from matter and motion. This led Nicolas Malebranche (1638–1715) to develop a theory of preformation by emboitement, according to which the germ cells contain, fully formed, the organism. During the seventeenth century, preformation offered a way of accommodating the view that mechanistic laws were insufficient as explanations of the construction of living organisms from unorganized matter. Pre-existence of the organism also avoided the atheistic and materialistic implications of a mechanistic epigenesis, by allowing that all organisms were preformed by the creator. Preformation was widely embraced by the beginning of the eighteenth century. Pierre-Louis Maupertuis (1698–1759), the Comte de Buffon (1713–81) and Needham took up the defence of epigenesis in mid-century, challenging preformationism. All three expanded the range of mechanisms available to include attractive forces. Faced with the problem of explaining the emergence of organization, Maupertuis attributed intelligence and memory to the smallest living particles. On the basis of experiments performed with Needham, Buffon proposed that the development of organisms depended on ‘penetrating forces’ analogous to gravity and magnetic attraction. Needham concluded that there was a ‘vegetative force’ which was the source of all the activities of life. These are vitalistic proposals, which make sense only within a mechanistic programme.
Similar problems persisted throughout the eighteenth and nineteenth centuries. Though Berzelius was mechanistic when faced with physiology, the production of organic form seemed to defy chemical explanation. He thus suggested there was a vital force differing from inorganic elements and regulating development. Charles Bonnet (1720–93), on the other side, was an enthusiastic champion of preformationism. He discovered parthenogenesis in the aphid, concluding that the female germ cell contained wholly preformed individuals, though he allowed that it need not be in exactly the form in which it exists in the adult organism. Beyond this he saw no explanation, emphasizing that the current state of physical knowledge does not allow any mechanical explanation of the formation of an animal. Bonnet embraced no vital forces, and therefore needed some primal organization.
At the end of the nineteenth century, analogous controversies resurfaced, though transformed and subject to experimental investigation. In investigating development, Wilhelm Roux (1831–1924) initiated an experimental version of Entwicklungsmechanik in support of internal determinants of development. He embraced a ‘mosaic’ theory of development, according to which the hereditary determinants are distributed in a qualitatively uneven way within the fertilized egg. As the cell divides, the daughter cells are genetically differentiated and these differences explain the differentiation of organisms. In 1888, Roux described experiments designed to test the idea of embryonic self-differentiation. At the first cleavage in the development of a frog, he destroyed one blastomere with a hot needle. In about 20 per cent of the cases, the remaining blastomere continued to develop, and it developed into half an embryo. He concluded that blastomeres develop independently, depending primarily on their internal constitution. This supported the view that development was controlled by material that was successively divided among the cells of the organism. This material, he thought, determined the growth of the organism in a fully mechanical form. In 1891, Driesch performed what seemed at first to be a very similar experiment, but with dramatically different results. Using sea urchins, he separated the blastomeres at the two-cell stage. Each blastomere developed into a smaller but complete blastula. He saw this result as inconsistent with Roux’s mechanistic account and, in particular, as inconsistent with the idea that division of the cell involved a division of the ‘germ’ controlling development. Since the blastomeres have the ability to develop into complete organisms, there could not be the kind of internal differentiation and control Roux had observed. Driesch initially sought external epigenetic factors to explain development. He came to see development as the response of a living organism rather than a mechanically predetermined process. He did not deny that physical and chemical processes are manifested in development, but held that the timing of development requires some special explanation. Physical laws thus place constraints on possibilities, but leave the actual outcome underdetermined. The connections were not immediately made, but Driesch was eventually led to a teleological and vitalistic view of development which he thought could explain developmental patterns.
Vitalism now has no credibility. This is sometimes credited to the view that vitalism posits an unknowable factor in explaining life; and further, vitalism is often viewed as unfalsifiable, and therefore a pernicious metaphysical doctrine. Ernst Mayr, for example, says that vitalism ‘virtually leaves the realm of science by falling back on an unknown and presumably unknowable factor’ (1982: 52). C.G. Hempel, by contrast, insists that the fault with vitalism is not that it posits entities which cannot be observed, but that such explanations ‘render all statements about entelechies inaccessible to empirical test and thus devoid of empirical meaning’ because no methods of test, however indirect, are provided (1965: 257). The central problem is that vitalism offers no definite predictions. Neither complaint has much historical credibility. Many vitalists were in fact accomplished experimentalists, including most notably Pasteur and Driesch. Moreover, vitalists took great pains to subject their views to experimental test. Magendie, for example, insisted on the importance of precise quantitative laws. Vitalism, as much as mechanistic alternatives, was often deeply embedded in an empirical and experimental programme. Typically, vitalists reacted to perceived inadequacies of mechanistic explanations; in many cases they rightly recognized that the forms of mechanism, materialism or reductionism advocated by their contemporaries were undercut on empirical grounds. In the end, though, their own proposals were supplemented by empirically more adequate mechanistic accounts.
WILLIAM BECHTEL
ROBERT C. RICHARDSON
Descartes, R. (1637). "Discourse on the Method," in J. Cottingham, R. Stoothoff, and D. Murcoch, eds., The Philosophical Writings of Descartes, volume 1, 109-76. Cambridge: Cambridge University Press, 1984.
Descartes, R. (1664). "Treatise on Man," in J. Cottingham, R. Stoothoff, and D. Murcoch, eds., The Philosophical Writings of Descartes, volume 1, 799-108. Cambridge: Cambridge University Press, 1984.