A frog lives, and moves its members, for half an hour after its head is cut off; nay, when the body of a frog is divided in two, both the anterior and posterior extremities preserve life and a power of motion for a considerable time….
A young cock, whose head Dr. Kaau suddenly cut off with a sharp razor, as he was running with great eagerness to his food, went on in a streight line 23 Rhinland feet, and would have gone farther, had he not met with an obstacle which stopped him…
A viper, after being deprived of its head and intrails, moved towards a heap of stones in a garden where it used to hide itself….
REDI informs us, that a land tortoise, whose brain he extracted by a hole made in its scull, in the beginning of November, lived till the middle of May following…1
In 1763, the Scottish physician Robert Whytt cited a series of (quite disturbing) experiments in an effort to prove that there is a soul, and that its powers operate throughout the bodies of living things. The fact that decapitated animals continued to “live” indicated to Whytt that their souls lingered in their bodies; they were therefore still, “in some sense, alive and endued with feeling.”2 If not for the power of “feeling” that exists throughout the body of an animal, he reasoned, how could the headless chicken keep running, or the mutilated viper return to its den? Whytt could imagine no other explanation for the motion of animals than this — and so he proposed that the muscles, ligaments, and nerves of living creatures are imbued with and animated by a “sentient principle,” differentiating their flesh from mere inanimate material.
Whytt’s essay on animal motion was just one entry in a prolonged debate in 18th century Europe over what moved man — that is to say, the source of motion in living things. On one side were the mechanists, who believed that the universal laws of nature were responsible for all motion and explained the world in terms of predictable interactions between material entities. This included even the human body, whose operation would be largely indistinguishable from that of an elaborate machine (see the previous entry in this series for more on mechanism). Whytt’s theory of the “sentient principle,” which he identified with the soul, was intended as a death blow to this mechanistic view. He wrote:
The true Physiology, therefore, of the human body, not only serves to confute those Philosophers, who, rejecting the existence of IMMATERIAL BEINGS, ascribe all the phenomena and operations in nature to the powers of matter and motion; but at last, like all other sound Philosophy, leads up to the First Cause and supreme Author of All, who is ever to be adored with the profoundest reverence by the reasonable part of his creation.4
Whytt joined a growing group of dissenters who claimed that only the power of the spirit could explain the movements of the body. Life had an immaterial component, they argued, which could not be reduced to physical matter. This was known as animism, the theory of a soul central to all bodily activities. To support their position, the animists mobilized empirical proof, as Whytt did above, but they also appealed to the wisdom of the ancients, whose spiritual knowledge could never be superseded by crude mechanical description. As I described previously, animism drew from a long and well-established Aristotelian tradition.
Mechanism privileged materiality and animism privileged spirituality, but both doctrines were asking the same fundamental questions. For thinkers in the 18th century, life was motion. Accordingly, to discover the cause of motion was to discover the cause of life.5 This meant that even something as simple as lifting one’s arm could inspire heated controversies surrounding the intersecting roles of the body, spirit, reason, and God in making that action possible. As such the interlocutors all assumed they were discussing something crucially important — that the answer to their debate would have important ramifications not only for science, but also for faith, ethics, and politics.
The typical narrative, established at the end of the 18th century, suggests that the debate between the mechanists and animists concluded amicably in the form of a compromise. In place of either alternative, the most fashionable theory of life in 1800 had become vitalism, a new, more robust system that avoided the pitfalls of its predecessors. Charles Louis Dumas was perhaps the first to describe vitalism as a sort of mediation:
[Vitalism] did not derive all of the manifestations of life from either matter or the soul. Rather, it derived them from a capacity, lying in the middle of both. This capacity differentiated itself from one and the other through specific characteristics; it ruled, directed and ordered all of life’s activities. The material body did not determine it, nor was it animated and enlightened by spiritual activity or by the intellectual powers of essential rationality.6
Vitalism refused to reduce life to any one component, neither pure matter nor pure spirit. As we will see, it depended on the theory of a “living principle,” as it were, a capacity that was neither material nor immaterial, that organised life’s activities in ways unique to it. For its time, this new theory was more true to empirical data, moral and religious sensibility, and common sense. The supporters of vitalism were therefore convinced that life science had successfully progressed from two imperfect and competing sets of truths to a single, better and more “true” form of truth in vitalistic thought.
But this narrative is misleading, for it misses the point of the shift that took place in the latter half of the 18th century. The debate over the nature of motion in living things, which had once commanded the attention of scientists and philosophers alike, was never allowed to reach a conclusion. Instead, it was simply set aside for an entirely different set of questions. Alongside the emergence of “vitalism” (and later on, “organicism”) was a new question of “life,” centered not on motion but on organization, function, unity, and difference.7 These days, it is rare for vitalism to be mentioned at all, and even rarer for it to be taken seriously as a scientific theory. But the story of its origins reveals something important about the questions we ask regarding the meanings and truths of “life.” In that sense, it is the story of “life” as we know it.
Mechanism allowed for only two substances in the world. There was mind, the domain of the soul, of thought, and of rationality. Then there was matter, the physical stuff determined exclusively by the immutable laws of nature. Since the human body falls into the latter category, it is inert and dead on its own; most of its actions would therefore be described in terms of the interaction of mechanical parts from which it is composed. The only exception to this would come from conscious direction provided by the mind, which manipulates the body like a puppet. Thus the presence of the soul alone differentiates the “living” from the dead, but even so it has a limited effect on the body-machine.
Mechanistic science had more or less become the consensus view by 1700, but of course it failed to satisfy everyone. One prominent skeptic was Georg Ernst Stahl, a physician who maintained that the animistic theories of “classical traditions are far superior to modern mechanistic speculations.”8 For Stahl, to leave the body up to the “laws of nature” was to strip it of purpose or intention, leaving it purely to chance. But this is not how living creatures actually function. Stahl insisted that all the activities of the body are oriented toward a goal, an aim, or a purpose — in all of life one sees the power of a purposeful agent, and that is what makes it unique. Without the unifying “principle of life” — which Stahl called the anima, or soul — the body would have nothing to hold it together and keep it in harmony.9
At first, Stahl’s theses failed to find widespread recognition among scientists. His critics portrayed him as a crude and conservative thinker, dismissing outright his reactionary pleas to return to more traditional forms of knowledge. They were not wrong to do so; Stahl’s animism regarded the spirit as the exclusive source of motion in living things, and so he tended to reduce all physiological processes to mere effects of the soul. This led to the absurd and counterproductive conclusion that the only proper goal of medicine is to heal the soul, the one source of all illness in the body.
But a new generation of skeptical minds would seize the potential in Stahl’s ideas for a thorough reformulation of life science, one that would avoid the reductive tendencies of mechanistic thought. Most of all they appreciated Stahl’s unification of body and mind, his restoration of intention and purpose to the organism, and his theory of an active “life principle” that would ensure life’s harmony. Moreover, Stahl eliminated what was least worthwhile about mechanism — the theory of lifeless, inert matter — without forfeiting the realization that living organisms have a knowable, mechanical structure. Rather than denying mechanism altogether, the Stahlians would stress that life is not exclusively mechanical — that there is something more to it that the mechanists had missed.11
Whytt was one of several animistic thinkers who sought to integrate Stahl’s ideas with the findings of mechanistic science. Unlike Stahl, Whytt did not portray reason, thought, or centralized control as defining characteristics of the soul. Instead, he argued that muscles fibres themselves are independently capable of “sensation” without requiring direction from the mind, as illustrated by decapitated animals. And unlike the mechanists, Whytt postulated a “sentient principle” inherent to all organic matter, the source of both voluntary and involuntary motion. His theory oscillated between mentalistic, when he insisted on the universality of “feeling,” and mechanistic, when he described the predictable reactions of the nervous system to external stimuli. The “sentient principle” was an immaterial “soul,” but it still followed a set of consistent and knowable laws. Whytt had created what one might call “animistic mechanism,” a synthesis that many scholars have erroneously labeled a form of vitalism.12
Unlike vitalists proper, Whytt’s primary concern remained the source of motion in the living organism. Other scientists around the same time presented hypotheses similar to Whytt’s, but with different aims and methods, distinguishing them as vitalists rather than “animistic mechanists.” This is perhaps most apparent in the works produced by the Montpellier school in France, one of the most influential early sources of vitalist thought. In particular, one Théophile de Bordeu would firmly establish the core ideas of vitalist physiology, namely, the notion of “sensibility,” organizational structure, and functional orientation.
For Bordeu, just as for Stahl, organic creatures are driven by a unique force that directs them towards particular ends, ensures their internal harmony, and organizes their bodies in ways that cannot simply be described as mechanical. In his first major work in 1751, Bordeu called this force “sensibility,” and used it to explain how glands respond to irritation by secreting fluids, a reaction that could not come about by mere mechanical pressures.13 The way he described this force seems quite similar to Whytt’s theory of a “sentient principle” everywhere in the body:
Each organic part of the living body has nerves which have a sensibility, a particular kind or degree of sensation. This sensibility makes the life of the nerves.14
However, in using the word “sensibility,” Bordeu did not literally mean that all body parts have the ability to “sense” or “feel,” as Whytt had claimed. Instead, “sensibility” was a provisional label for the processes unique to life which could not be replicated in a machine; Bordeu did not pretend to know how or why glands were capable of moving in response to stimuli.15 This is his first point of departure from his predecessors, who had been preoccupied with the general question of motion in living creatures; Bordeu circumvented the question by equating life with a force called “sensibility” and rendering motion a secondary effect.16 This signaled a broader transition that would take place across the 18th century life sciences.17
If all the parts of the body have their own “sensibility,” Bordeu suggested, then they are also capable of functioning as independent entities. The glands, for instance, operate on their own and are unique in how they respond to stimuli. This shows that the organs do not require a “central command,” like the soul, to fully direct and organize all bodily functions. Nor could there be a universal set of mechanical laws that would explain how all body parts operate, since each one has a specialized set of functions and abilities. The diversity of life’s functions would be the foundation of “vitalist” physiology. Every organ has a life of its own — they are neither cogs in a machine nor puppets of the spirit.
But wouldn’t this hypothesis also fall prey to Stahl’s original critique of mechanism (and indeed Bordeu’s theories were quite explicitly mechanical)? That is, how would the living organism maintain its unity or coherence without something to unify it? Bordeu provided his answer to this potential criticism in the form of a famous, and undeniably compelling analogy:
I compare the living body, in order to properly grasp the particular action of each part, to a swarm of bees which cluster together, and hang from a tree like a bunch of grapes… Each part is, so to speak, not quite an animal, but a kind of independent machine which contributes in its way to the general life of the body.
The application [of this metaphor] is easy: the organs of the body are connected to one another; they each have their district and their action; the relations between these actions, the resulting harmony, is what constitutes health.18
For Bordeu and his colleagues, the internal harmony of the living organism did not require a singular entity to unify it. Instead, harmony was determined by the relations between organs, each one contributing in some way to the overall health of the body. Thus the human body is like a swarm of bees. Out of many, one.
Another Montpellier physician, Jean-Joseph Ménuret, would later refer to the unique constellation of relationships between body parts as the “animal economy,” a system of internal organization that had gone unnoticed by the doctrines of mechanism and animism. He summarized his position as follows:
The body should only be considered as an infinite assemblage of small, identical bodies, similarly alive and animated, each possessing a life, an action, a sensibility – [that is] both a specific, particular interaction and movement, and a common, overall life and sensibility. All parts contribute in their own way to the life of the entire body, and as such they reciprocally correspond to and influence one another.20
The vitalist conception of life was fundamentally about organization: the nature of individual organs’ interrelationships and interdependencies, whose overall “economy” produces a “life and sensibility,” not some singular and overarching force. The “vital principle” of vitalism was therefore not unified, but diffused throughout the body, manifesting diverse characteristics in the organs. Just as important as the entire organism were the vital functions of the organs, each one with a “life” of its own while contributing to the “life” of the whole. Their functions were not reducible to mind or matter; they were potentialities specific to organic material, products of its innate characteristics and “sensibilities.”
Bordeu’s image of the bee-swarm was — and is — captivating because it suggests that the human is a plural, not “unitary-monarchic” being. Whereas an influential physician like William Harvey had earlier regarded the blood as the “the chief Palace and Court of the Soul,” Bordeu rejected the monarchic metaphor in favor of viewing the human more as a “federation of organs.”21 When he declared that we are not fundamentally under the control of a centralized mind, spirit, or consciousness, and that our activities are not all directed towards a unified goal, there is no denying that he was saying something political. Many of his contemporaries expressed similar views, “dethroning” the soul, reason, and God from their positions of authority in animism and mechanism, in favor of a self-governing idea of the organism. The king was dead, but life went on.
Indeed, politics were important points of reference in debates over the nature of life and its organization. The emerging life sciences were impacted deeply by factionalism — royalists, republicans, and revolutionaries in Western Europe all had a vested interest in it, even more so after the French Revolution began in 1789. In particular, the history of vitalism appears closely related to that of radical enlightenment politics (although vitalists themselves were not always so forward-thinking). In light of this, several scholars have recently presented vitalism as a “more humane alternative to the allegedly oppressive mechanical natural philosophy”, and it is not hard to see why.22 Vitalism presented a view of the human being that is organized from the bottom-up rather than top-down; its constituent parts are self-organizing, yet driven by goals and with purpose; together they form a whole that is irreducibly diverse yet ideally harmonious. As a framework for understanding human relationships and society, one could certainly do worse.
Although there is much to be appreciated in all this, it has to be said many ostensibly positive characteristics of vitalist thought would be forgotten, dismissed, or downplayed, especially in the 19th century. We will explore this development in subsequent parts, but for now it is worth noting that vitalism did make a number of lasting contributions to the life sciences (and the question of “life” more generally).
First, vitalists described a “living principle” or “vital force” that was unique to organic matter and could not be found anywhere else. To the modern ear this might sound like baseless metaphysical speculation, or even new-age babble — and indeed vitalism has precisely that reputation today. But in its original formulation, vitalist claims were a great deal more cautious; the idea of “vital forces” like “sensibility” was only meant to indicate the processes unique to organic matter, whose existence was purely empirical. Vitalism was therefore heir to the Newtonian empirical legacy, only instead of an ill-defined gravitational force intrinsic to matter, they postulated imminent forces of life. In 1802, William Heberden perfectly summarized the vitalist creed: “to living bodies belong many additional powers, the operations of which can never be accounted for by the laws of lifeless matter.”23
Of course many biologists today would not subscribe to this statement. Two centuries later, it is no longer controversial to say that organic material abides by the same mechanical principles of physics and chemistry as everything else. As it turned out, talk of “vital forces” was useful only to the extent that we were ignorant of life’s material causes. Nonetheless, biology as a discipline remains remains focused on the unique processes and characteristics of the organic, albeit without alluding to a special force or principle. Indeed this is precisely what differentiates biology from other fields of inquiry: the study of what is particular to life. It is not incidental that the term “biology” was first coined around 1800, differentiating it from the sciences of nonliving things.24
Second, the “living principle” of vitalism was also crucially a principle of organization. If living things were composed of numerous organs with diverse functions, then the organism is to be understood in terms of the process of coordinating and regulating that diversity. Thus the vitalist telos inheres in multiple levels: there are the aims of individual molecules, organs, or organ systems, and then there are the aims of the organism as a whole. This is at once pluralistic, holistic, and teleological. Life is “more than the sum of its parts.”
Finally, vitalism contributed to a shift in the terms of debate over the nature of life. The original abiding concerns of the conversation — the origin and quality of motion — were no longer considered essential. The more pressing questions were now the nature of life’s various functions, how it was organized, and how its organization related to the health of the organism. In order to accommodate these questions, a “new mechanism” was developed (and remains popular even now.) But the mechanism of today is not at all the mechanism of Descartes. It is no exaggeration to say that vitalism contributed to a drastic shift in the life sciences in the second half of the 18th century.
At this point we are very close, chronologically and thematically, to where we began at the introduction to this series: the question of the “meaning of life” as it emerged in the early 19th century. Vitalism’s conception of a “living principle,” its focus on purposeful organization, and its awareness of life’s diverse functions all played a role in the formulation of that question. None of these ideas were new, but taken together they would inaugurate the kind of philosophical speculation over the “meaning of life” with which we are familiar today. But we are not there quite yet. After all, vitalism threatened to take the unity of the organism and splinter it into pieces. For the “organicists,” the task at hand was clear — to piece life back together again.
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- If you’re interested in the historical question of the “meaning of life,” I previously wrote an introductory essay on the subject. For more on the “mechanical” philosophy, see the previous entry in this series.
1 Robert Whytt, An Essay on the Vital and Other Involuntary Motions of Animals (Edinburgh: Hamilton, Balfour, and Neill, 1751), 384-387.
2 Ibid., 388.
3 Andreas Vesalius, De Humani Corporis Fabrica Libri VII (Basel: Froben, 1543).
4 Whytt, 392.
5 Hubert Steinke, Irritating Experiments: Haller’s Concept and the European Controversy on Irritability and Sensibility, 1750-90, Irritating Experiments (Brill Rodopi, 2016),20.
6 Translation provided by Hans Reill, 120.
7 This can also be seen in the substitution of “organic” for “animate” as an adjective describing life. Andrew Cunningham, “The Pen and the Sword: Recovering the Disciplinary Identity of Physiology and Anatomy before 1800: II: Old Anatomy—the Sword,” Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences 34, no. 1 (March 1, 2003): 58.
8 Georg Ernst Stahl, “Ueber den Unterschied zwischen Organismus und Mechanismus,” in Georg Ernst Stahl, Sudhoffs Klassiker der Medizin 36 (Leipzig: Johann Ambrosius Barth, 1961), 49. Quoted in Reill, Vitalizing Nature, 126.
9 Jacques Roger, The Life Sciences in Eighteenth-Century French Thought, ed. Keith R. Benson, trans. Robert Ellrich (Stanford University Press, 1997), 343-344.
10 For a summary of Stahl’s influence on later thinkers, see Reill, 127. For an overview of Stahlian animism, see Steinke, 185-193.
11 Sergio Moravia, “From Homme Machine to Homme Sensible: Changing Eighteenth-Century Models of Man’s Image,” Journal of the History of Ideas 39, no. 1 (1978): 45–60.
12 This is probably because they consider vitalism to be nothing more than a theory speculating the existence of a “vital force” (which in Whytt would be the “sentient principle”).
13 Moravia, 53.
14 T. de Bordeu, ‘Recherches Anatomiques sur la Position des Glandes et sur leur Action’ (Paris, 1751), Œuvres Complètes de Bordeu (2 vols, Paris: Caille and Ravier, 1818), i, 420. Translation provided in Steinke, 204.
15 “Although Bordeu referred frequently to this force he did not attempt to explain its action, noting only that we know that it exists from its actions in the body.” Shirley Roe, “The Life Sciences,” in Cambridge History of Science. Early Modern Science. Vol 4, ed. Roy Porter (Cambridge University Press, 2003), 405.
16 Moravia, 55-56.
17 Other notable scholars who participated in this shift include Albrecht von Haller, Hieronymous Gaub, Caspar Friedrich Wolff, Johann Friedrich Blumenbach, William Cullen, and John Hunter. For an overview of this development, see Steinke, 199-214.
18 Théophile de Bordeu, “Recherches anatomiques sur la position des glandes et leur action” (Paris: Quillau père 1751). Translation provided by Charles T. Wolfe and Motoichi Terada, “The Animal Economy as Object and Program in Montpellier Vitalism,” Science in Context 21, no. 4 (December 2008): 550-551; parentheticals and brackets included in the original translation have been omitted here.
19 F. G. Jenyns, A Book About Bees, (London, W. Gardner, Darton, & co., 1886), front cover.
20 Jean-Joseph Ménuret, “Pouls (Méd. Econom. anim. Physiol. Séméiot.),” Encyclopédie vol. XIII (Paris: Briasson, 1765), 240a. Translation provided by Wolfe and Terada, 549-550.
21 William Harvey, Anatomical Exercitations Concerning the Generation of Animals, (London: Macdonald, 1653), 278; Moravia, 56.
22 Veronika Szántó, Did Harrington’s cats catch Harvey’s chick? Vitalistic imagery in early modern republican political theory (History of European Ideas, 43:6, 2017), 571. One recent example valorizing vitalist thought is Reill, Vitalizing Nature.
23 Quoted in Theodore M. Brown, “From Mechanism to Vitalism in Eighteenth-Century English Physiology,” Journal of the History of Biology 7, no. 2 (1974): 183-184.
24 Roe, “The Life Sciences,” 416.