Home » Early Modern Philosophy » The Princess and the Philosopher: Princess Elisabeth of Bohemia’s Denial of Substance Dualism

The Princess and the Philosopher: Princess Elisabeth of Bohemia’s Denial of Substance Dualism

George P. Simmonds
Oxford Brookes University


I: The Princess and the Philosopher

René Descartes was a prominent seventeenth-century philosopher well credited for his philosophic contribution to the Early Modern period (Anderson, 2004). Often referred to as the ‘father of modern philosophy’ (Skirry, 2004), Descartes is perhaps remembered most for his metaphysics, namely his substance dualism, which posited that mind and material are two distinct substances, each wholly separate and independent of the other.

Descartes’ Meditations, published 1641, was the first vessel of Cartesian dualism. Descartes was not, however, the first to introduce the subject; dualism can, like so many things, be traced back to the ancient Greeks. Plato’s Phaedo distinguishes the mind from the body on the basis of its close ‘affinity’ with the Forms, non-physical entities separate from the material world (Plato, 1997; pp.49-100). Later philosophers embraced this dualistic school of thought, also. Aquinas, for instance, believed the soul to be an immaterial substance, a substance which required embodiment to interact with the physical world (Aquinas, 1981; pp.363-70). It is clear that the topic of dualism had been well ventilated by the seventeenth century, and it seems certain that Descartes studied these ideas before formulating his own. Prior to the Meditations, dualism’s focus was on the intellect as the main problem for materialism. Descartes switched this emphasis to human consciousness (Robinson, 2012). This emphasis is generally considered more appropriate for contemporary debate on mind and body since consciousness is not so easily accounted for by neuroscience. For this reason, as well as the depth to which he explored his metaphysics, modern writers on dualism would be hard-pressed to omit Descartes from their bibliographies.

Descartes’ motivations for writing on the mind-body distinction can be assumed to have been philosophical in nature, but this would not discount his theological agenda. Descartes’ theology played a large role in his philosophical works, and though God featured only briefly in Cartesian dualism, mind-body independence is closely linked and congruent with a belief in God. The idea of the soul existing independently of the material world was consistent with the theologies of the time, and thereby attracted many of Descartes’ contemporaries (Hart, 1996; pp.265-7). It should not, however, be assumed that dualism enjoyed universal popularity among Descartes’ followers. His ideas on dualism spurred a vigorous materialist response which led many who agreed with Descartes’ elsewhere to lean further towards a physicalist school of thought (O’Connor & Robertson, 1997).

Princess Elisabeth of Bohemia was among these physicalist dissidents. Though she appeared to agree with much of Descartes’ work elsewhere (his mathematics and geometry in particular), as far as his ideas on dualism are concerned, Elisabeth presented a contestation which stands still today as perhaps the most effective rebuttal of Cartesian ideas (Rozemond, 1999; pp/.426).

In what follows I will argue in favour of Elisabeth’s materialist doubts. I will first attempt to expound Descartes’ substance dualism, before presenting the subsequent refutation posed by Elisabeth. I will, thereafter, illustrate Descartes’ theory of interaction, as delineated in both his correspondence with Elisabeth and the literature it inspired. Finally, I will approach this defence critically and in character of Elisabeth’s scepticism.

II: Descartes’ Substance Dualism

Descartes holds that the mind and body are two distinct substances. This is not to suggest that he was denying the existence of the brain, or the body’s influence on our thought processes; he was a physiologist, after all, and possessed an extensive knowledge of the body’s functions (Descartes, 2003). As mentioned in the section above, when he speaks of the mind-body divide he is drawing distinctions between our body and our consciousness. This is the key difference between that part of us which simply receives sensory data engendered by the rainbow, and the part which actually experiences it.

In his Discourse Descartes presents his most elementary case for substance dualism, the Doubt Argument, whereby he discovers that ‘while [he] could pretend that [he] had no body, and that there was no world and no place for [him] to be in, [he] could not for all that pretend that [he] did not exist.’ From this he concludes that ‘[he is] a substance whose whole essence or nature is simply to think, and which does not require any place, or depend on any material thing, to exist’ (Descartes, 1999; 6:32-3). The Doubt Argument, then, presents the following:

  • I can doubt that my body exists.
  • I cannot doubt that I exist as a thinking thing.
  • I, a thinking thing, am not identical with my body.

Unfortunately for Descartes, however, this argument was not well received: some claim there to be a missing premise without which the conclusion is not adequately supported, while others believe it ‘fallacious’ in its heavy dependence on ‘conceivability based on ignorance’ (Hatfield, 2014; §3.4). Either way, whether by a missing premise or the fact that Descartes could be simply ignorant of his own materiality, the Doubt Argument was believed insufficient (Rodis-Lewis, 1999; pp.69).

Descartes expands this thesis in his Meditations. He claims the world contains two and only two substances, each of which retains its own ‘essential property’ (Howard, 2012; §2.1). Descartes defines a substance as something which ‘can exist by itself, that is without the aid of any other substance’ (this is to say they are ontologically independent) (Descartes, 1991; pp.159). Matter is therefore a substance, since it relies on nothing else. Take the example of a vase and the colour red: we may conceive of the vase existing independent of its colouring, yet the colouring itself cannot exist free of the vase. Ergo the vase is of substance and the colour is not. There is an ‘intuitively intelligible sense in which its colour and shape cannot exist apart from the vase,’ yet the vase seems to be ‘something that exists in its own right’ (Kim, 2011; pp.33). Mind is a substance of a different sort: it exists independently of any other substance, namely matter, yet has properties and engages in activities suited to its immateriality (i.e. judging, sensing and willing). The main conclusion of the Sixth Meditation is that the mind and body are really distinct and conceptually separable, that ‘for any minds and bodies that are united, it is counterfactually possible that they be separated’ (Cunning, 2004). This is commonly termed the ‘Real Distinction.’

But what does he mean by ‘essential property’? According to Descartes, the essential property of something is that ‘property without which the thing cannot exist’ (Kim, 2011; pp.38). This is to say that we are unable to conceive of something stripped of its essential property, since it would cease to be that which we think it to be. Thus, the essential property of matter is to be extended, for it is implausible to conceive of a material object lacking extension (Ibid.; pp.40). (We can conceive of the element of gold in many different forms, for instance, yet not lacking the very quality of being a material thing). It is not, however, essential to our existence that we are extended (as seen in the Doubt Argument), only that we are thinking. Descartes insists that from our capacity to conceive of the mind functioning as a disembodied entity we may conclude that extension is not essential to its existence—and that it is therefore immaterial. To summarise, then, in the Sixth Meditation Descartes determines that the essential property of the mind is thought, and that the essential property of matter is extension—and that these facts entail their independence (Descartes, 1996; 7:78).

This should not be seen as the sole argument for Descartes’ substance dualism, for many alternatives have been provided by both Descartes himself and those who supported him. The above argument is, however, among the simplest and most straightforward of cases for the mind-body divide, and leads most conveniently to Elisabeth’s subsequent critique.

Of course Descartes needed to bring this theory into context. Though he made the above efforts to separate the mind from the body, by way of their incompatible essential properties, he was compelled also to conceive of their union, a union lodged within the human being. This is of course vital to dualism, since human beings claim possession of both their minds and their bodies, and observe in everyday life the key interaction between the two. Hence, Descartes heralds the human as a uniquely ‘composite being’ within whom an interactional ‘union’ of mind and body is located (Kim, 2011; pp.34). It is in this respect that Cartesian dualism appeals to Early Modern theology, since it is compatible with the Christian idea of the soul, undying and separate from the physical body.

Here we may conclude in laying down the three major tenets of Cartesian substance dualism:

  • There are two fundamentally distinct substances in the world, mental substance and material substance.
  • The ‘essential property’ of mental substance is thought; the ‘essential property’ of material substance is extension.
  • Within the human being there is a union of mind and body whereby the mind (mental substance) and body (material substance) interact.

III: Elisabeth’s Scepticism

Princess Elisabeth of Bohemia was something of an epistolary philosopher. Though she employed her ‘remarkable and wide-ranging critical philosophical acumen’ (Shapiro, 2013; pp.3) with little hesitation, Elisabeth did not undertake a philosophical work of her own. The letters she wrote the academic figures of her time are all that remain of her ideas, and indeed constitute the only evidence for her philosophical interest. These resources are, however, considered extensive enough to piece together a comprehensive position (Emmet, 1989; pp.96).

The issues she raises with regard to Descartes’ substance dualism are evident in their correspondence. She poses to him a simple query, and in so doing exposes a serious problem for Descartes and his philosophy. ‘I beseech you to tell me,’ she writes in 1643, ‘how the soul of man (since it is but a thinking substance) can determine the spirits of the body to produce voluntary actions’ (Atherton, 1994; pp.11). Here she is referring to the interaction of the mind and the body, a phenomenon proposed by Descartes to occur within the human being. The thrust of her argument is Elisabeth’s contention that something lacking extension, namely the mind, cannot affect something that is extended, such as the body.

Elisabeth’s line of argument might not seem to challenge Descartes’ theory directly, since it takes issue only with the interaction of the mind and the body. Contrary to this, however, the problem of interaction casts serious doubt on Cartesian thought, for unless the mind and the body can interact, the very concept of dualism becomes questionable. When the mind longs for the company of a friend it interacts with the body to pick up the phone; and when the body senses danger it compels the mind to respond. This apparent interaction is difficult to deny, and if Descartes is to account for it, he must formulate a means by which mental and physical substance can cooperate.

The reasons behind Elisabeth’s doubts are based on observations of the physical world. She notes that ‘every determination of movement happens from an impulsion of the thing moved,’ meaning, in terms of physics, movement of a physical entity is inspired only by the movement of another. In all things conceivable, movement appears to require such things as ‘contact,’ ‘figure,’ and ‘surfaces.’ Of course, the question of how the mind could cause the body to move would be unproblematic to Descartes if he had not ‘entirely excluded extension from [his] notion of the soul’ (Ibid.). Since such things as contact and force seem incompatible with an immaterial thing, one could here accuse Cartesian dualism of being illogical.

Some have interpreted Elisabeth’s inquiry to concern itself more with the Real Distinction than the problem of interaction (Shapiro, 1999; pp.506). It is worth noting that Elisabeth, in her initial writing, assumed Descartes already had an explanation for the interaction of the mind and body, and that her misunderstandings lay instead with the nature of the mind. It would appear that Elisabeth regarded the alleged interaction between material and non-material substance as so absurd that she instead supposed Descartes’ explanation of the mind was incomplete. Since his response did little to revise her conception of the mind, however, Elisabeth’s position may still be considered one which concentrates on Cartesian interactionism.

IV: Descartes’ Response

Descartes acknowledges Elisabeth’s problem of interaction, admitting it possesses the ‘greatest of justification in sequel to the writings I have published,’ but does not appear to hold it in much serious regard (Ibid.; pp.13). He appeals to what he refers to as ‘primitive notions,’ fundamental ideas which ‘cannot be explained in terms of other more basic notions’ (Kim, 2011; pp.49). He mentions a number of these, though three are particularly relevant to his response:

  • The primitive notion of extension (including ‘figure’ and ‘movement’), which refers to the body.
  • The primitive notion of thought (including aspects of the ‘understanding’ and the ‘will’), which refers to the mind.
  • The primitive notion of the mind-body union (wherein the interaction of the mind and body occurs).

The notions relevant to the mind and body separately, Descartes claims, are made clearer by the use of reason and understanding. We come to understand the nature, and distinction, of mental and material substance through this understanding. The notion of the union, however, is made more clear by everyday perceptions, by ‘abstaining from meditating and studying things that exercise the imagination’ (Atherton, 1994; pp.18). What is meant here is that while we are able to discover things about the mind and body individually by way of philosophical inquiry, conversely such measures obscure the notion of the mind-body union. Instead the way we should seek to understand the mind-body union is by simple observation of their interaction, as would those ‘who never philosophize’ (Ibid.).

This confusion, Descartes proposes, is what carried Elisabeth to her misunderstanding. A vital quality of Descartes’ primitive notions is their applicability only to their appropriate objects—‘for when we wish to explain some difficulty by means of a notion that does not pertain to it, we cannot fail to make a mistake’ (Ibid.; pp.13). What he means here is that we cannot come to understand the nature of X by virtue of a primitive notion pertaining to Y, and vice versa. This is an important point, since this means we cannot come to understand anything of mind-body causation by way of our understanding of body-body causation (Monroy-Nasr, 1998). Descartes believes Elisabeth to have made this fallacious assumption.

This ‘primitive notion’ of the mind-body union may seem dubious, and indeed some have questioned whether a notion can be primitive if referring to two elements (Cottingham, 1985; pp.224), but a case can be made for Descartes’ argument. This lies in the ‘asymmetry’ of the mind and body: the mind may exact its causal powers only through the body, while the body is able to interact with other bodies independently. This qualifies the body as the ‘enabler of [the] mind’s causal powers.’ And from this view, if only faintly, the mind-body union does seem ‘essential’ to grasping the mind’s causal powers (Kim, 2011; pp.49). This concludes the Cartesian defence of the Elisabeth-Descartes correspondence.

V: Elisabeth’s Unremitting Scepticism

Elisabeth is unconvinced by Descartes’ response. She admits that ‘it would be easier for [her] to concede matter and extension to the soul, than the capacity of moving a body and of being moved, to an immaterial body’ (Atherton, 1994; pp.16). What she means here is that, despite Descartes’ conception of the ‘primitive notions,’ it is yet easier for her to grasp the concept of a material mind than it is to imagine the interaction of a material and non-material substance. Here can be seen Elisabeth’s partiality to the materialist school of thought, championed by the likes of Hobbes. It is clear that she is not persuaded by Descartes’ defence.

She willingly acknowledges that the senses illustrate the mind’s interaction with the body, but insists that ‘they fail to teach [her] the manner in which [the mind] does it.’ This is a valid criticism, since the mind and body appearing to be interact does not entail that they really are. Both Leibniz and Malebranche would confidently deny any such connection: Leibniz, the parallelist who believes the physical and mental realms move together in consonance without interacting, would not acknowledge the mind and body’s apparent interaction as proof of their union. Neither would Malebranche, the occasionalist who claims the perceived interaction the simple intervention of God. Descartes’ primitive notions do nothing to set his dualism ahead of these alternative ideas; and though the notions relating to the mind and body separately might be accessed by our reason, it appears committing to the notion of mind-body union involves a unreasonable degree of faith.

Descartes’ primitive notion of the mind-body union can, and was clearly viewed by Elisabeth to be, wholly circular in its reasoning. The only way to characterise the mind-body union is by way of a causal argument: This body belongs to me because my mind interacts with it directly; and, similarly, in order for changes to be made to my mind my body must first be altered. There can be no clearer or more ‘natural’ account of the mind-body union. But this interaction presupposes the primitive notion of mind-body union, which in turn can be explained only by this very interaction (Kim, 2011; pp.50). This circularity emphasises the element of faith essential to understanding Descartes’ mind-body union.

Elisabeth attempts to redress Descartes’ problem of interaction by suggesting that ‘there are unknown properties in the soul that might suffice to reverse what [Descartes’] metaphysical meditations…persuaded [her] concerning [the mind’s] inextension’ (Atherton, 1994; pp.20). She here explores the possibility of the mind possessing an extended aspect through which it is able to interact with the body without reference to the elusive primitive notion of the mind-body union. This suggestion is quickly retracted, however, with the realisation that such an aspect—extended and material—would have to possess intelligence, which Descartes ‘accord[s] to nothing corporeal’ (Ibid.; pp.16). This offering was probably the motivation behind Descartes’ later inclusion of the pineal gland: ‘Although the soul is joined to the whole body, there is yet in that a certain part [the pineal gland] in which it exercises its function more particularly than in others’ (Descartes, 1989; pp.17). This inclusion did little to alleviate Elisabeth’s doubts, however, and was later branded the ‘exercising [of] physiological ingenuity in an unsuccessful attempt to solve a fundamentally philosophical problem’ (Kenny, 2009; pp.225).

Elisabeth was torn between accepting Descartes’ substance dualism—and having to deal with the insurmountable problem of interaction (which she saw possible only through reforming the Real Distinction)—and admitting the mind extended properties. Considering Descartes’ weak argument for accepting the mind-body union, and his reluctance to remodel his conception of the mind’s inextension, Elisabeth’s rejection of his ideas appears to be well justified.

VI: Conclusion 

Despite Descartes’ great fame and renown, and Elisabeth’s general obscurity, it is—to many readers of Descartes—Elisabeth who ‘comes out of [this] debate with the upper hand’ (Pynn, 2012). The most obvious reason for this is that Descartes simply fails to provide an adequate response to her confutations. Upon noting the clear problem of the mind-body interaction, Elisabeth gives Descartes the choice of either amending his conception of the Real Distinction, of giving a full account of how the mind and body might interact, or of allowing the mind to be extended. He does not respond in any of these three fashions, and instead turns to notions for which he can provide neither justification nor explanation. His defence embraces an element of faith Elisabeth considers inappropriate, irrational, and above all unconvincing.


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  1. Budimir Zdravkovic says:

    Elisabeth’s argument is a very powerful argument to this day. It reminds me of the current arguments for revisionary materialism. She believes that phenomenal states (such as consciousness) will be reduced to psychological states (such as behavior) with partial revisions to the substance dualist position. It seems that her attempt to move the philosophy of mind in this direction is also one of the earliest attempts at a tangible theory of consciousness. An attempt that is still being pursued by current philosophers such as David Chalmers.

    • Yes, it’s true, and the almost petulant attitude she displays in her correspondence is one shared by a number of physicalist thinkers today. When Descartes proffers a hole in the physicalist theory of mind and presents his own, allegedly more conclusive system, Elisabeth scoffs and says ‘Yes, yes, dear – but it is equally if not more likely that we are simply overlooking something in the physical mind that’d put this all to rights.’ Philosophers are naturally quixotic and often leap to transphysical theories the moment the opportunity reveals itself to them. Elisabeth was no such philosopher: she was a woman of adamantine realism and was not easily led astray by her philosophical correspondents. I can’t help but admire her ever-present focus on morality, too – she had a wonderful proclivity to bring philosophical discussion down to an ethical bedrock and ask, often quite bluntly, ‘Now how does this affect morality?’ It was a question Descartes hadn’t hitherto considered, and it’s a question we are in many ways failing to ask now.

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