Philosophy of the Mind, Part VII
T.H. Huxley “On the Hypothesis that Animals are Automata, and its History”
Thomas Henry Huxley (1825–95) was a largely self‑taught comparative anatomist whose scientific work commanded wide attention in his own lifetime and beyond. He also involved himself in broader questions raised by science, including the theory of natural selection and evolution (which he championed early on), the place of scientific education and religious teaching, and most relevant here, the relation between mind and body.
In the nineteenth century, new techniques for storing and discharging electric charge made it possible to apply electric currents to dissected specimens, greatly advancing the study of the nervous system. Huxley’s essay reflects on the implications of these physiological discoveries for the philosophy of mind. He is an early defender of epiphenomenalism, the view that consciousness is a causal result of underlying physical processes but has no causal influence on them, like the way a shadow depends on the object that casts it, but does not affect the object.
Mechanism and Descartes
Huxley praises the seventeenth century as “one of the great epochs of biological science,” in which Harvey’s work on circulation and Descartes’ work on motion and sensation established the idea that the living body is a mechanism. He endorses one of Descartes’ key claims: that animals are “mere machines or automata,” and he quotes Descartes to this effect.
Descartes writes:
“No movement can take place, either in the bodies of beasts, or even in our own, if these bodies have not in themselves all the organs and instruments by means of which the very same movements would be accomplished in a machine.”
In other words, our bodies are composed of parts corresponding to the parts a suitably designed machine would need to produce the same movements. The key motive factor in Descartes’ physiology is the system of animal spirits, the subtle fluid whose motions transmit signals through the nerves. Many bodily movements do not depend on the mind at all — heartbeat, digestion, nutrition, respiration, spontaneous actions such as waking, walking, even singing, and protective reactions such as those involved in falling. In such cases, changes in the brain direct the animal spirits into the appropriate nerves; no corresponding mental act is required.
Thus Descartes asks:
“why should we be so much astonished if the light reflected from the body of a wolf into the eye of a sheep has the same force to excite in it the motion of flight?”
Huxley quotes Descartes’ distinction between actions “effected in us by the operation of the mind” and actions “which depend only on the animal spirits and the disposition of the organs.” On Descartes’ own account, animal behaviour belongs solely to the latter class, arising from the “continual affluence of animal spirits produced by the heat of the heart, which attenuates and subtilizes the blood.” We have no good reason, Huxley notes, to infer that animal actions are produced both by mind and by mechanism merely because human actions are; to do so is, as Descartes himself says, a “hastily concluded” argument.
Reflex action and “superior marionettes”
From this framework, Huxley infers that reflex actions show that highly coordinated, purposive behaviour can occur without consciousness or volition. Actions produced by a more refined mechanism , such as the mammalian nervous system , may be expected to be correspondingly more complex than those of a human‑made automaton, but they are still mechanical. On Descartes’ view, this suffices to explain any animal action; animals are like “a superior race of marionettes.”
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Huxley illustrates the force of the reflex model with a striking surgical case: the removal of the anterior division of a frog’s brain. After such an operation, the frog can remain in full bodily vigour but will sit motionless unless stimulated; under appropriate stimuli, it moves with precise and well‑coordinated muscular responses. Huxley argues that such experiments provide stronger support than Descartes’ own arguments for “the automatism of brutes: the machinery which is competent to do so much without the intervention of consciousness might well do all.” Similar lesions or diseases in humans can reduce a person to a condition comparable to that of the frog, again suggesting that complex behaviour can be driven by neural mechanisms alone.
Animal consciousness
Here Huxley breaks with Descartes. He rejects Descartes’ denial of consciousness to animals. First, he appeals to a doctrine of continuity: complex natural phenomena rarely arise abruptly but emerge through gradations. We see consciousness itself arise gradually in human development and in the transition from sleep to waking. Second, he points to anatomical parallels: animals possess brain regions corresponding to those in humans that subserve consciousness; in general, in both, “function and organ are proportional.” Huxley concludes that animals are conscious, though their consciousness is less intense than ours and, lacking language, they appear to have trains of feeling rather than trains of thought. Given the struggles of animal life, he even remarks that it might be better if Descartes were right, but he insists that he is not.
So Huxley accepts Descartes’ mechanism but not his denial of animal consciousness: animals are machines (automata), but conscious ones. Animal instinct is, on this view, simply the product of their “physical organization.” In particular, the nervous system “not only sets the rest [of the body] in motion, and co‑ordinates its movements … but is provided with special apparatus, the function of which is the calling into existence of those states of consciousness which are termed sensations, emotions, and ideas.”
Conscious automata and epiphenomenalism
Huxley then “turns Descartes’ argument on its head.” If animal movements can be explained by reflex motion alone, the same is true of human movements; we too are automata. Being pricked by a pin, for example, is, via the nervous system, the immediate physical antecedent of a state of consciousness, but the conscious feeling does not itself move the limb. Rather, it accompanies neural events that do.
Huxley notes that only two older views deny such a mechanistic connection: Occasionalism, according to which God continually intervenes to align mental and physical events, and the doctrine of Pre‑established Harmony, according to which God set up independent mental and physical series to run in parallel. He rejects both as incompatible with scientific explanation. We still lack a complete account of the causal chain, but it is reasonable, he maintains, to regard sensation as “the effect of molecular change.”
Just as in humans, animals’ “affections of their sensory nerves” produce “molecular changes in the brain” which in turn “evolve into corresponding states of consciousness.” This is the basic mechanism of their emotions and ideas. Memory, likewise, has a physical basis: each sensory impression leaves a trace in the brain, an “ideagenous molecule,” which later reproduces, in a weakened form, the state of consciousness originally produced.
Crucially, Huxley argues that there is no evidence that states of consciousness cause the neural changes that lead to muscular motion. His frog experiment illustrates that the same bodily movements can occur “without volition, as with it.” Volition in the frog can therefore be regarded as “nothing but a concomitant” of the molecular changes in the brain that form part of the causal chain producing motion. More generally, animal consciousness appears to be a “collateral product” of bodily processes, “as completely without any power of modifying that working as the steam‑whistle which accompanies the work of a locomotive engine is without influence upon its machinery.” Volition marks physical changes, but does not make them happen.
Freedom, volition, and souls
Within this framework, Huxley defends a compatibilist conception of freedom: to act freely is to act in accordance with one’s desires. In this sense a greyhound freely chases a hare; it is both a machine impelled to the chase and, in the ordinary sense, acting freely. Volitions are products of the underlying mechanism and “do not enter into the chain of causation of [our] actions at all.”
The argument up to this point, Huxley notes, is compatible both with the view that animals have souls and with the view that they do not. Animal consciousness might be a direct function of material changes, in which case there is no soul; or, if there is a soul, it might be an indirect product of material changes, “related to the body as the bell of a clock to the works,” with consciousness corresponding to the sound the bell emits when struck.
Extending the argument to humans
What makes Huxley controversial is his insistence that the conclusions drawn from the study of brutes apply equally to human beings. This seems to threaten us with “fatalism, materialism, and atheism.” Huxley accepts the mechanistic conclusion but denies that the alarming labels follow.
He claims there is no proof that any state of consciousness causes changes in the motion of bodily matter. Mental conditions are “simply the symbols in consciousness of the changes which take place automatically in the organism”; the feeling of willing an act is the conscious symbol of the brain state that is the immediate physical cause of that act. We are, in his phrase, “conscious automata”: free only in the compatibilist sense, and parts of an unbroken chain of causes and effects composing the world.
Huxley concludes that the consequences of this view should “be left to take care of themselves.” Consequences indicate how seriously we should take a conclusion, not whether it is true. He denies being a fatalist, arguing that the strong notion of necessity required by fatalism is not demonstrable from physical science. He denies being a materialist, on the grounds that his own conscious experience is undeniable and not reducible to pure matter in any straightforward way. Nor is he an atheist, since he sees no purely natural explanation of why the universe exists at all, and thus leaves room for a creator.
References:
Descartes, René. “Objections to the Meditations and Descartes’s Replies.” Early Modern Texts, translated by Jonathan Bennett, 2017, https://www.earlymoderntexts.com/assets/pdfs/descartes1642_2.pdf.
Huxley, Thomas. “On the Hypothesis That Animals Are Automata, and Its History.” Collected Essays of T. H. Huxley (Clark University), Clark University, 1874, http://aleph0.clarku.edu/huxley/CE1/AnAuto.html.
