Chapter 2 Animals and Machines: Changing Relationships in the 17th & 18th Centuries

We begin our journey by looking at the early intellectual precursors to the idea of self-reproducing machines, dating from the seventeenth and eighteenth centuries. These works form part of a much older exploration of the relationship between living organisms and machines—a tradition with origins in tales of automata from across the ancient world (e.g. (Solla Price, 1964), (Cohen, 1966), (Kang, 2011, pp. 14–22), (Mazlish, 1993, pp. 31–34)).5

2.1 Animals as Machines, Machines as Animals

In the early seventeenth century, René Descartes argued that animals are machines, and that humans alone possess a mind with subjective consciousness:

“… it seems reasonable since art copies nature, and men can make various automata which move without thought, that nature should produce its own automata much more splendid than the artificial ones. These natural automata are the animals.”

— René Descartes, Letter to Henry More, 5 Feb. 16496

Having separated the concepts of life and mind, Descartes’ programme for understanding living phenomena envisaged “the reduction of living things to a class of processes which are entirely accessible to general physics” (Carter, 1991, p. 208). Because he viewed animals as machines, and their reproduction as a purely physical process,7 the general idea of self-reproducing machines can be seen as inherent in Descartes’ approach. However, his writing about reproductive processes was always with reference to natural, rather than artificial, automata (that is, animals and the human body). Nevertheless, his arguments inevitably led some to pursue the analogy and imagine the idea of self-reproducing artificial automata.

There is an anecdote retold several times in the recent literature about a conversation between Descartes and Queen Christina of Sweden (e.g. (Freitas Jr & Merkle, 2004), (Sipper & Reggia, 2001), (Amos, 2006)).8 Upon hearing Descartes’ views on animals as machines, Christina is said to have responded that “she had never seen her watch give birth to baby watches” (Ortega y Gasset, 1941, p. 19). We have been unable to find an authoritative original source for this anecdote, and it is probably apocryphal.9 However, such ideas were certainly in the air by the second half of the seventeenth century; in 1683, for example, the French academic Bernard Le Bovier de Fontenelle wrote:

“Do you say that beasts are machines just as watches are? Put a male dog-machine and a female dog-machine side by side, and eventually a third little machine will be the result, whereas two watches will lie side by side all their lives without ever producing a third watch.”

— Bernard Le Bovier de Fontenelle, Letter XI “to Monsieur C…”, 168310

While Descartes sought to understand all living phenomena apart from the human mind in terms of material properties, other philosophers of the time adopted a completely materialist perspective, in which all phenomena, including the human mind, were to be explained in terms of the properties of matter. One of the most prominent statements of materialism of the period came from the English philosopher Thomas Hobbes; where Descartes had suggested that living beasts are machines, Hobbes in his 1651 book Leviathan suggested that mechanical automata possess “an artificial life”:

“For seeing life is but a motion of limbs, the beginning whereof is in some principal part within, why may we not say that all automata (engines that move themselves by springs and wheels as doth a watch) have an artificial life? For what is the heart, but a spring; and the nerves, but so many strings; and the joints, but so many wheels, giving motion to the whole body, such as was intended by the artificer?”

— Thomas Hobbes, Leviathan, 1651 (Hobbes, 1651, p. 7)

The seventeenth and eighteenth centuries witnessed the creation of progressively more sophisticated automata, accompanied by further materialist comparisons between humans and machines. A chief proponent of these materialist views was Julien Offray de La Mettrie, best known for his work L’homme machine (Man a Machine) published in 1747 (La Mettrie, 1747); detailed accounts of his work and of the general intellectual development of such ideas in this period can be found elsewhere (e.g., (Riskin, 2016), (Kang, 2011)).11 By the second half of the eighteenth century, the incredulity shown by de Fontenelle and others in the preceding decades regarding the possibility of machine reproduction had become a little more subdued. In 1769, the French philosopher Denis Diderot pushed the discussion of materialism even further in a series of three dialogues, later published collectively under the title Le Rêve de d’Alembert (Diderot, 1769). Comparing the operation of the human mind to the oscillations and resonances of a harpsichord’s strings, one of the participants in the first dialogue remarks:

“And so if this sentient and animated harpsichord was now endowed with the faculty of feeding and reproducing itself, it would live and, either on its own or with its female partner, give birth to little harpsichords, living and resonating.”

— Denis Diderot, Conversation Between d’Alembert and Diderot, 1769 (Diderot, 1769)12

Diderot uses this image in the context of proposing a materialist description of the development of a sentient animal from a germ cell; machine reproduction was not the focal point of the passage. Nevertheless, it is perhaps the first published work where the idea of a self-reproducing machine is defended in a dialogue rather than being immediately dismissed as absurd.

2.2 Mechanism and Design

The increasingly common comparison of animals to machines in the seventeenth and eighteenth centuries is also reflected in the growing use of what is now known as the watchmaker analogy in arguments for the existence of God.13 The general form of such arguments is as follows: If you were to study the intricate mechanisms and organisation of a watch and observe how they operate to perform the function of telling the time, you would naturally assume that the watch had been designed by a skilled watchmaker who had the intention of creating an artefact to perform that function; equally, if you consider the immeasurably more complicated mechanisms and organisation of the human body, you should similarly conclude that it has been designed by an ultra-intelligent designer, or God.

In recent times the watchmaker analogy has become most closely associated with William Paley and his 1802 publication Natural Theology (Paley, 1802), which we will discuss shortly. Paley is of particular interest in the current context because he raised the idea of a self-reproducing watch in his argument. However, we can trace the origins of even this use of the idea of self-reproduction in the watchmaker analogy back to the seventeenth century.14

The first printed example of the analogy with an allusion to self-reproduction that we are aware of appears in the English clergyman Thomas Doolittle’s 1673 publication The Young Man’s Instructor and the Old Man’s Remembrancer (Doolittle, 1673).15 In a chapter of the book entitled “That there is a God”, Doolittle sets out the following argument:

“Can any thing that is not, work or do any thing? No.

Can any thing be before it is? No.

But that which doth make any thing is before that which is made? Yes.

Then if any creature had made it self, it would have been before it was, and it would have acted when it was nothing: but that is impossible: is it not? Yes.

Then every thing that was made, was made by something that is and was not made: was it not? Yes.

And that which is, and was not made, must be God? Yes.

When you see a good going Watch, a well tuned musical Instrument, a fair built House, or several Letters in a Printing-house, to be put in due order to make significant Words, you conclude, that there was some Workman that did all these things? Yes.

So when you see Sun, Moon, and Stars, the Earth, the Sea, Men, Beasts of the Field, Birds of the Air, being they could not make themselves, you conclude, there must be one that is the first cause of all things that are made, or else they could never have been. … do you not? Yes.

Then there is no more reason you should doubt, whether God is, than whether you are: is there? No.

— Thomas Doolittle, The Young Man’s Instructor, 1673 (Doolittle, 1673, pp. 31–32)

We see here that Doolittle argued that even a self-reproducing organism (a creature that “made itself”) must have been originally made by an eternal creator.16 The argument that self-reproduction does not mitigate the need for an original creator was later made more explicitly by William Paley in his Natural Theology (Paley, 1802). Paley (1743–1805), like Doolittle, was an English clergyman and philosopher, and Natural Theology was his final published work, appearing in 1802. In it we also find the first explicit and protracted discussion of the concept of a self-reproducing artificial (as opposed to biological) machine.

Paley’s discussion of the watchmaker analogy in Natural Theology begins in Chapter 1 where he asks us to imagine coming across a stone while walking in the country. If we were asked how it had come to be there, it would be perfectly reasonable, he argued, to assume it had always been there. However, the situation would be different, he suggested, if we came across a watch rather than a stone. By inspecting the watch and discovering it to consist of many intricate parts precisely arranged so as to perform the function of displaying the time, we would hardly conclude that, like the stone, it had lain there forever. We would surely conclude, he argued, that there must have been a skilled craftsman or artificer who “comprehended its construction, and designed its use” (Paley, 1802, p. 8).

In Chapter 2, Paley extends the argument by supposing we discovered that, in addition to telling the time17

“… [the watch] possessed the unexpected property of producing, in the course of its movement, another watch like itself … That it contained within it a mechanism, a system of parts, a mould for instance, or a complex adjustment of laths, files, and other tools, evidently and separately calculated for this purpose …”

— William Paley, Natural Theology, 1802 (Paley, 1802, p. 11)

He asked what effect such a discovery would have upon our previous conclusion. His answer was that it would not affect our conclusion, for we would still have to account for the design and construction of the original watch in the series of self-reproducing watches: “There cannot be design without a designer” (Paley, 1802, p. 12).

In his argument, Paley was thinking about watches making exact copies of themselves (i.e. self-reproduction without variation, or standard-replicators). He got very close to imagining a progressive series of small changes over a lineage of watches when he asked the further question: in what circumstances would the fact that the watch is self-reproducing change our conclusion about its origins? “If the difficulty [of a design requiring a designer] were diminished the further we went back [in the lineage of self-reproducing watches], by going back indefinitely we might exhaust it. And this is the only case to which this sort of reasoning applies” (Paley, 1802, p. 13).

However, Paley did not make the final step of imagining an evolutionary sequence of small changes from simple beginnings. In his watch analogy with self-reproduction but lacking variation “[n]o tendency is perceived, no approach towards a diminution of this necessity [of requiring a designer]” (Paley, 1802, p. 13). He concluded that, even when considering self-reproduction, “[t]he thing required is the intending mind, the adapting hand, the intelligence by which that hand was directed” (Paley, 1802, p. 14). The step of replacing an intelligently-directed adapting hand with the adapting hand of evolution by natural selection would have to wait another sixty years for the publication of Darwin’s On the Origin of Species and the imagination of Samuel Butler (see Sect. 3.1).18

* * *

As we have seen in this chapter, comparisons between animals and machines in the seventeenth and eighteenth centuries led to the first glimmerings of the idea of machine self-reproduction. As time progressed, we see the notion being used in the literature with fewer caveats attached. As outlined in Sect. 1.6, this work represents the first major step in the development of thinking about self-replicators. Specifically, discussions during this period were about the fundamental question of whether a machine could construct a copy of itself—that is, to use our terminology, whether it is possible to design a standard-replicator. This step, combined with the introduction and widespread use of increasingly complex machinery during the Industrial Revolution of the late eighteenth and early nineteenth century, and the publication of Darwin’s theory of evolution by natural selection, set the stage for the second major step—the idea that machines might not only be able to reproduce but also evolve. The development of this second step—the emergence of the idea of an evo-replicator—is the subject of the next two chapters.


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  1. More detailed accounts of lifelike automata emerge in medieval Europe and the Middle East, particularly from the thirteenth century onward (e.g. (Riskin, 2016), (Kang, 2011)).↩︎

  2. Translated text quoted from (Cottingham, 1991, p. 324).↩︎

  3. Descartes’ views on reproduction and growth developed over his lifetime (Des Chene, 2000, pp. 32–33), with the most mature account set out in De la formation de l’animal published posthumously alongside Traite de l’homme in 1664 (Roe, 1981, p. 4). He conceived the process as one of regeneration and conservation of form, which followed general laws of nature, progressing from the initial stages of the “extremely volatile and expansive seminal mixture” of the fertilised ovum, with growth constrained and guided by the particular conformation of the ovum’s membrane (Carter, 1991, p. 211). However, his account was ultimately unsatisfying (e.g. (Roe, 1981, pp. 4–5), (Des Chene, 2000, pp. 33–35), (Fouke, 1989, pp. 368–370)). An interesting discussion of Descartes’ views in the context of other seventeenth century explanations of biological reproduction can be found in (Fouke, 1989), and discussion of further development of thought on these matters in the eighteenth century can be found in (Duchesneau, 2014) and (Roe, 1981).↩︎

  4. And (Levy, 1992, p. 16) has “the queen of France” as the protagonist.↩︎

  5. In addition to conducting an extensive search of primary and secondary literature, we have also contacted many leading historians of science and philosophy who specialise in Descartes, Queen Christina or early reproductive biology (see acknowledgements at the end of the book), but most of them had not heard of this anecdote, none knew of an original source and most thought it sounded apocryphal. During our search, the earliest mention we found of the anecdote was in a 1924 text in Spanish by the philosopher José Ortega y Gasset (Ortega y Gasset, 1946, p. 610): “A Descartes, que sostenía la naturaleza mecánica de los cuerpos vivos, ya decía Cristina de Suecia que «ella no había visto nunca que su reloj diese a luz relojitos».” An English translation of this work appeared in 1941 (Ortega y Gasset, 1941, pp. 18–19): “Queen Christina of Sweden remarked to Descartes, who upheld the mechanical nature of living beings, that she had never seen her watch give birth to baby watches.”↩︎

  6. (Fontenelle, 1752, pp. 322–323), translated text quoted from (Roe, 1981, p. 1).↩︎

  7. Descartes’ and Le Mettrie’s views were by no means universally accepted, however. For detailed coverage of the controversies that continued to rage in early modern philosophy on the relationship between organisms and mechanisms, see, for example, (Nachtomy & Smith, 2014), (Duchesneau, 2014), (Fouke, 1989), (Riskin, 2016).↩︎

  8. English translation by Ian Johnston (source:, quoted with permission. Note that Johnston’s translation uses the phrase “little keyboards” at the end of this quotation, which we have replaced with “little harpsichords”. The original French version uses the same word “clavecin” (harpsichord) throughout the text. The original French version, together with an account of the history of these dialogues, can be found in (Lough, 1953, pp. 83–98).↩︎

  9. But note that the history of such arguments dates back much earlier, at least as far as Cicero in the first century BCE (Jantzen, 2014).↩︎

  10. A text that bears many similarities to Paley’s in the use of the watchmaker analogy was published over eighty years prior to Natural Theology by the mathematician Bernard Nieuwentyt in a 1716 publication in Dutch, which was translated into English in 1718 (Nieuwentyt, 1718). Some have argued that Paley plagiarised Nieuwentyt’s work (see (Jantzen, 2014, pp. 120, pp.69–71)). However, Nieuwentyt’s argument did not include the idea of a self-reproducing watch which was present in Paley’s work.↩︎

  11. Another early version of the watchmaker argument appears in a lecture preached by John Howe in 1690 (Calamy, 1838, p. 1060).↩︎

  12. We also see in this quote that Doolittle, with his image of “several Letters in a Printing-house, to be put in due order to make significant Words,” is using a version of what is now known as the “tornado in a junkyard” argument, made popular in recent times by Fred Hoyle (Hoyle, 1983, p. 19), and frequently used by present-day creationists in arguments for the existence of God. John Howe’s publication from around the same time as Doolittle, mentioned in the previous footnote, also used a similar image (Calamy, 1838, p. 1060). For a full discussion of the history of such arguments, from antiquity to the present day, see (Jantzen, 2014).↩︎

  13. Note that Paley, like Diderot before him (Sect. 2.1), is using the image of a self-reproducing machine without dismissing it as an obviously absurd or impossible idea.↩︎

  14. A tantalising “near miss” in terms of earlier candidates for thinking about the evolution of self-reproducing machines is Erasmus Darwin (1731–1802), a contemporary of William Paley and grand-father of Charles Darwin. He is well known for his early ideas on the theory of biological evolution, set out in Zoonomia: Or the Laws of Organic Life (E. Darwin, 1794). Perhaps less widely known, Erasmus Darwin was also interested in designing machines and mechanisms, examples of which included devices for producing multiple copies of handwritten text and also the design for an artificial mechanical bird, powered by compressed air and featuring a fully specified wing movement cycle (King-Hele, 2005). However, despite his combined interests in evolution, mechanical copying machines and artificial organisms, we have found no evidence that he thought about the possibility of self-reproducing machines. Further information and pictures of Darwin’s designs are available on the Revolutionary Players website. A model based upon Darwin’s design for an artificial bird was recently commissioned for public display at his former home (now a museum) in Lichfield, England (see↩︎