Elisabeth writes to Descartes after having read the Meditations or, as she refers to it, the Metaphysics (AT III 661/S 62). In the Sixth Meditation, Descartes outlines his account of and arguments for mind-body substance dualism, as well as his account of the union of the mind and body.7 At the core of Descartes’ substance dualism is the claim that the mind and body are two really distinct substances. However, in order to fully appreciate Elisabeth’s objections to Descartes’ substance dualism we need to disentangle a number of different positions (all of which Descartes seems to have held).

In this section I outline four distinct components of Descartes’ dualism: the real distinction component; the differing natures component; the principal attribute component; and the property-type component. It is important to distinguish between these different components of Descartes’ view to understand Elisabeth’s various objections. In the course of explaining the four distinct components of Descartes’ view, I also consider his two main arguments for dualism: the real distinction argument and the differing natures argument. I then consider his account of union from the Meditations, as it is central to two of Elisabeth’s objections.

The first aspect of Descartes’ substance dualism is the real distinction component—the view that mind and body are distinct substances capable of existing apart. The real distinction component of Descartes’ dualism, as I shall understand it, is simply a claim about the ontological independence of mind from body and body from mind in the sense that neither depends on the other for its existence. The mind does not need the body to continue to exist and the body does not need the mind to continue to exist (though it may very well depend on the relation to the soul in order for a particular body to be a human body or to be Elisabeth’s body). As I shall understand the real distinction component, no claims are made about the natures of the respective distinct substances. So, it is consistent with the real distinction component that the two really distinct substances have the same type of nature, for example, two different yard signs in the same yard that are made of the same types of materials are really distinct.

The real distinction component of Descartes’ dualism is clearly on display in the real distinction argument. Descartes claims: ‘I have a clear and distinct idea of myself, in so far as I am simply a thinking, non-extended thing; and on the other hand I have a distinct idea of body, in so far as this is simply an extended, non-thinking thing’ (AT VII 78/CSM II 54). In Descartes’ words, the conclusion of this argument is: ‘it is certain that I am really distinct from my body, and can exist without it’ (AT VII 78/CSM II 54).

The second aspect of Descartes’ dualism is the differing natures component—the view that minds and bodies have wholly distinct natures. For Descartes, the complete and total nature of the mind is thinking and the complete and total nature of the body is extension. On this view, minds and bodies have entirely distinct natures. This component is also on display in the real distinction argument when Descartes argues that he—his soul—is a purely thinking and non-extended thing while his body is a non-thinking and extended thing (AT VII 78/CSM II 54). It is also central to the differing natures argument for dualism from the Sixth Meditation. This argument revolves around the claim ‘that there is a great difference between the mind and the body, inasmuch as the body is by its very nature always divisible, while the mind is utterly indivisible’ (AT VII 85–86/CSM II 59). The main point here is that mind and body have incompatible natures: the former is indivisible and the latter is divisible. And, because he takes divisibility and indivisibility to be incompatible, he concludes that the mind and the body must be distinct substances. As Descartes claims: ‘This one argument would be enough to show me that the mind is completely different from the body, even if I did not already know as much from other considerations’ (AV VII 86/CSM II 59).

The next two components are the principal attribute component—a substance and its principal attribute (or its nature) are identical and the property-type component—minds have only mental properties and bodies have only physical properties. I elaborate on this below, but in brief Descartes holds that each substance has a principal attribute that constitutes its nature, and ultimately each substance just is its principal attribute. So, on this view minds just are thinking things and bodies just are extended things. A particular mind and its thinking are identical. Descartes makes this commitment most explicit in the Principles of Philosophy (written after the relevant part of the correspondence), but it is implicitly present in the Meditations and more importantly we shall see Elisabeth objects to (or perhaps better: asks for clarification about) this component of his view. The property-type component holds that souls have only mental properties and bodies have only physical properties. I also develop this below, but for Descartes, a mental mode or idea is a determinate way of existing as a thinking thing. Elisabeth presses Descartes on this feature of his view, specifically on whether souls can have physical properties.

Elsewhere in the Sixth Meditation, Descartes discusses the connection between the soul and the body: ‘Nature also teaches me, by these sensations of pain, hunger, thirst and so on, that I am not merely present in my body as a sailor is present in a ship, but that I am very closely joined and, as it were, intermingled with it, so that I and the body form a unit.’ He adds that ‘If this were not so, I, who am nothing but a thinking thing, would not feel pain when the body was hurt. … For these sensations of hunger, thirst, pain and so on are nothing but confused modes of thinking which arise [exorti] from the union and, as it were, intermingling of the mind with the body’ (AT VII 81/CSM II 56). Descartes seems to be claiming that the mind and body causally interact with one another, and that sensations are caused by the body.8

In what follows, I argue that Elisabeth offers objections to all of the above components of Descartes’ dualism except the real distinction component. Specifically, she suggests that a proper understanding of the nature of our soul shows that the other three components are false. She rejects the claim that the mind and body in fact have entirely different natures. She suggests, instead, that certain phenomenon can best be explained by allowing that the mind may have a partially extended nature or at least have some physical properties. She accepts, I think, Descartes’ real distinction argument as proving that a mind as a pure thinking thing could exist, but she rejects, based on several cases, the claim that our minds are in fact only thinking things.

Elisabeth begins her series of objections by asking about the interaction of mind and body:

It is perhaps no surprise that the problem of whether minds and bodies can interact has been the focus of most treatments of and responses to Elisabeth’s objections (most notably Descartes’ response to Elisabeth). After all, it begins the exchange and Elisabeth clearly introduces the problem. However, she immediately continues:

Before getting into my discussion of the three distinct objections Elisabeth makes through this stage of the correspondence, there are a few aspects of Elisabeth’s initial framing of the objection I want to emphasize. First, in passage 1, it seems that Elisabeth’s motivation for the concern is revealed in the very important parenthetical remark. Her worry about the two substances interacting is predicated on the worry that the soul is only a thinking substance. She does not motivate the worry by suggesting that mind and body subsist apart, that mind and body are two different types of substances in general, that minds and bodies have different natures per se, or any substantive principle about the nature of causal relations. Rather, the worry is about Descartes’ conception of soul as only a thinking thing and some specific features of what such interaction would require. Further, she does not ask about interaction in general, but asks about how a soul can cause voluntary action. This suggests that it is not simply their capacity for causal relations in general that concerns Elisabeth, but also causal relations involving enough control to warrant voluntary action.9

After raising the problem, Elisabeth immediately asks Descartes for a more precise definition of the soul as a substance separate from its action.10 Elisabeth does not ask Descartes to explain how minds and bodies interact or for an account of their union, but specifically asks Descartes for a more precise definition of the soul as a substance separate from its action. She then claims the soul and thought being inseparable is difficult to prove in (i) the mother’s womb and (ii) in fainting spells. From the initial stage of the debate, Elisabeth’s objections are focused on the nature of the soul.

Elisabeth returns to issues with Descartes’ account of the soul in future letters. Elisabeth’s objections are brief and condensed, and it will be helpful to cite the key text here and then proceed to disambiguate the various objections in subsequent sections. In a letter from June 10, 1643:

From her July 1, 1643 letter:

She continues:

In each of these passages, Elisabeth’s focus continues to be on the nature of soul. In the next three sections I argue that throughout these letters, Elisabeth offers at least three distinct problems for Descartes’ account: (i) the causal interface problem; (ii) the vapors problem; and (iii) the principal attribute problem.

The first objection Elisabeth offers, and the one that has received the most attention, is the causal interface problem. Elisabeth begins her first letter with this worry. In passage 1, she asks Descartes ‘how the soul of a human being (it being only a thinking substance) can determine the bodily spirits.’ She then goes on to note that ‘all determination of movement happens through the impulsion (la pulsion) of the thing moved, by the manner in which it is pushed by that which moves it, or else by the particular qualities and shape of the surface of the latter.’ She adds, ‘Physical contact is required for the first two conditions, extension for the third. You entirely exclude the one [extension] from the notion you have of the soul, and the other [physical contact] appears to me incompatible with an immaterial thing.’

As noted in the introduction, what I am calling the causal interface problem is well-documented and is the problem many scholars focus on when engaging the problem of interaction. I am calling this problem the causal interface problem to avoid ambiguity. Elisabeth invokes this problem and suggests that bodies are only able to be moved in three ways: by impulsion of the thing moved, by being pushed, or by the qualities and shape of the surface of the object moving them. She then argues that soul fails to meet any of these conditions for moving a body. The first two conditions, she explains, require physical contact between the two objects standing in a causal relation. The third requires the potential cause to have extension. So, Elisabeth objects to Descartes’ account of the causal relation between the mind and body by noting that the soul—at least a purely thinking soul—lacks the necessary features to interact with the body in such a way as to cause motion. Elisabeth is not objecting that two distinct substances cannot interact, nor even that two dissimilar substances cannot interact. Rather, she puts forward a concern about the specific features of the body and what is required to move bodies, and claims that Descartes’ account of the soul lacks the necessary features to stand in such a relationship to the body. As she specifies in passage 1, the problem is with the ‘notion you [Descartes] have of the soul.’ Elisabeth is careful here to specify the problem is not with the notion of a soul per se, but Descartes’ notion of the soul. The causal interface problem is the problem of whether the soul—as described by Descartes—is able to determine bodily motion given the specific features of souls and bodies that seem to preclude their ability to causally interact.11

After Elisabeth first offers the casual interface problem, she proceeds to ask Descartes, in passage 2, for a ‘more precise definition of the soul than the one you give in your Metaphysics.’ She does not ask for a better account of causation, nor for help understanding the union, nor for an account of other ways in which bodies could be moved. She specifically asks for a more precise definition of the soul. Up to this point in the exchange, only one direction of causal interaction is considered, soul-to-body.

She returns to the issue of the ability of the mind and body to interact in passage 3. There she notes ‘it would be easier … to concede matter and extension to the soul than to concede the capacity to move a body and to be moved by it to an immaterial thing.’ Here Elisabeth still focuses on the soul and notes issues with causal interaction in both directions, both the soul’s ability to move the body, and the soul’s ability to be moved by a body. She adds that with respect to the capacity for a soul to a move a body, if it ‘is achieved through information,’ then ‘it would be necessary that the spirits, which cause the movements, were intelligent.’ Elisabeth then claims that Descartes denies this capacity to anything corporeal. She adds that Descartes has shown the possibility of the soul being moved by a material thing. Elisabeth’s acknowledgment of the possibility that the soul be moved by a material thing would be surprising on the view that Elisabeth intends to offer an a priori argument against such interaction. In any case, she goes on to offer a new problem for Descartes, what I shall call the vapors problem, to which I now turn.

Elisabeth introduces the vapors problem in passage 3 right after acknowledging that Descartes has shown that it is possible that bodies can causally move the soul. She claims: ‘it is altogether very difficult to understand that a soul, as you have described it, after having had the faculty and the custom of reasoning well, can lose all of this by some vapors, and that, being able to subsist without the body, and having nothing in common with it, the soul is still so governed by it.’12 Like the causal interface problem, the vapors problem fundamentally concerns causal interaction between souls and bodies. Unlike the causal interface problem, the vapors problem does not concern whether souls and bodies are able to interact at all, but rather a type of mental phenomena and its effects that Elisabeth suggests Descartes’ account cannot explain.

In the above quote, Elisabeth invokes the concept of vapors (vapeurs). The vapors, a (supposed) type of aliment, are understood as a purely physical phenomena and are ‘“exhalations” in the stomach or spleen’ that are said to cause ills like hypochondria and mental imbalance (Broad 2004: 23–24). Symptoms of this supposed ailment include weak pulse, dimness in the eyes, and foam at the mouth.13 The specifics here are less important for my argument than the general idea that the vapors are a supposed physical phenomenon that have a certain type of mental consequence. This mental consequence is not simply that they cause specific thoughts, for example, the thought that ‘there is distress in my spleen’, but that they seem to influence the way in which we think.

Based on the relevant passage (cited above), Shapiro suggests that

While Shapiro’s account is illuminating, I think that Elisabeth’s concern here is different. She is not worried about the individual subsistence of the mind and body, in the sense of the real distinction component outlined above. Rather, she thinks that phenomena like the vapors are a problem for Descartes’ account of the nature of the soul, specially, a conception of the soul as only a thinking thing.

Elisabeth’s main worry here is about both the nature and lasting impact of physical stimulus on the soul. She worries that a soul could lose the faculty of thinking well on account of a physical ailment. While she does then note an aspect of her worry is that the soul subsists without the body, she adds, importantly, that the problem is motivated not simply by the soul subsisting without the body, but also by the soul having nothing in common with the body. On my view, this latter claim is central to Elisabeth’s concern. Elisabeth is not worried about whether the mind can subsist independently from the body to which it is united; as I read the correspondence, her commitment to their real distinction never wavers. Rather, she is worried about whether a mind which subsists independent of the body and is only a thinking thing with nothing in common with the body could be so governed by a body. Elisabeth’s concern, it seems to me, is not only that physical phenomena can alter the content of our thought, which I think she would cede to Descartes, but that his account cannot explain physical phenomena’s ability to affect the way we think and the lasting nature of the impact in our thought.

In order to illuminate Elisabeth’s concern, I think it is helpful to distinguish between three types of cases:

The three sorts of cases noted above help illuminate Elisabeth’s worry. Disconnection cases seem to be the easiest for Descartes to explain. This phenomenon could be easily explained with a physical issue in the communication between soul and body. And, any subsequent panic and/or other mental phenomena that result could be caused by the soul. Whether such cases persist or are relatively transient will depend on whether the physical issue causing the disconnect persists.

Though perhaps less clear, it also seems that Descartes’ account works for cases like the distraction cases. In these cases, one might be able to suggest that we are still thinking properly, or maintain the faculty of clear thinking, but are distracted by the frequency, vivacity, and diversity of stimuli. While they may be so overwhelming that it is hard to think clearly or exercise one’s faculty on account of the distraction, one does not seem to lose the faculty. Imagine someone trying to think through a difficult math problem while being surrounded by cacophonous sounds and periodic strobe lights. She would, it seems, have a difficult time doing so. However, we might think this is in virtue of the environment being distracting and not a fundamental change in the nature of the thinking itself. We need not posit some fundamental alteration to the nature of thought to explain this case, but only frequent and distracting external stimuli. Once more, the persistence of this impact on the mind can be explained even in instances where the external causes of the stimuli cease (e.g., the cacophonous sounds), if there is a change in the pineal gland that makes such distractions persist.

Finally, we get to vapors cases. These are the sorts of cases I think Elisabeth has in mind, not only in the nature of the effects, but also in their ability to last and persist. Vapors cases, at least temporarily—though perhaps permanently—seem to undermine the faculty of thinking clearly in a way distraction cases do not. In Elizabeth’s words, these cases undermine ‘the faculty and the custom of reasoning well.’ In these sorts of cases, one is not simply distracted or fed disconnected ideas, nor does one feel like one’s body no longer responds to the mind. Rather, one’s thought can slow down and the very nature of the thought itself seems undermined. Take a case where due to blood loss, one loses the coherency of one’s thoughts, feels light-headed, and becomes disoriented with decreased consciousness. At least intuitively, this sort of case cannot be accounted for just by the soul being afforded different contents or by being distracted.15

Elisabeth’s worry is that Descartes’ account of the soul cannot accommodate vapors cases. Elisabeth notes two aspects of the worry: given Descartes’ dualism, (i) how a soul could have the faculty and custom of reasoning well, and then lose that on account of physical causes, and (ii) how the soul, being able to subsist without the body and having nothing in common with it is so governed by it. If thought is purely immaterial, then why would a bodily event change our ability to reason well? Elisabeth’s claim is that Descartes’ account cannot explain why a cause would affect the way we think or the nature of our thought or why such effects persist long after the physical cause has left. Note that in cases like the blood loss case, it is not simply that blood loss is the cause of one’s soul thinking of certain things. In such cases, the physical effect does not merely cause one to focus one’s attention to the wound, nor does it merely cause one to be distracted. Rather, it changes the way one thinks. And, such events often influence thinking well after the external stimuli have gone. A single traumatic physical event can have a lasting effect not only on what one thinks, but how one thinks long after the physical trauma. Simply causing a change to the pineal gland does not seem sufficient in these cases.

I take Elisabeth’s concern about the vapors to be similar to the blood loss case. If vapors are a purely physical phenomenon, then at best, given Descartes’ account, they would be able to cause the soul to have certain thoughts at certain times. They would not be capable of fundamentally altering the nature and quality of the thought itself nor would they be able to have the type of lasting effect after the physical cause has left. Elisabeth’s account is not that the vapors undermine an account of dualism in the sense of a real distinction, but they undermine Descartes’ conception of the soul as only thought. She is worried about how a soul, being only a thinking thing that is independent of the body and that has nothing in common with the body, can be affected by a body in the precise way that it often is. If the soul has physical properties or has an extended component or aspect, then an external physical cause could fundamentally change the internal constitution of the soul. And the soul could easily retain internal changes (or literally retain some properties) from external stimuli. Elisabeth suggests that one could much more easily explain both the nature and the lasting effects of certain physical causes by positing physical aspects of the soul. Indeed, in some cases, like fainting, one seems to lose thought altogether. This type of case leads to the third and final worry of Elisabeth, the principal attribute problem, to which I now turn.

Elisabeth raises the principal attribute problem in her first letter to Descartes, where she requests a definition of the soul ‘separate from its action, that is, from thought.’ I take Elisabeth here to be engaging with claims like those Descartes makes in the Second Meditation: ‘But what then am I? A thing that thinks. What is that? A thing that doubts, understands, affirms, denies, is willing, is unwilling, and also imagines and has sensory perceptions’ (AT VII 28/CSM II 19). While Descartes is not explicit in the Meditations about the principal attribute component of his dualism, passages like these suggest that he identifies the activity of thinking with the essence of mind. He makes this commitment explicit in the Principles of Philosophy where he offers a more careful account of substances, attributes and modes.16 While the Principles is not the text that Elisabeth is engaging and was not yet written at the time of Elisabeth’s letters that are the focus of this paper, the precision used by Descartes in that text will be helpful for illuminating Elisabeth’s objections and so I focus on the Principles here.

Descartes defines ‘substance’ in article 51 of the Principles: ‘By substance we can understand nothing other than a thing which exists in such a way as to depend on no other thing for its existence’ (AT VIIIa 24/CSM I 210). Though he sometimes uses them interchangeably, Descartes makes an important distinction between ‘mode’ and ‘attribute’. Descartes claims: ‘we employ the term mode when we are thinking of a substance as being affected or modified; when the modification enables the substance to be designated as a substance of such and such a kind.’ He adds ‘in the case of created things, that which always remains unmodified—for example existence or duration in a thing which exists and endures—should be called not a quality or a mode but an attribute’ (AT IXb 26/CSM I 211–12). Modes of a substance, according to Descartes, are ways substances can be ‘affected or modified.’ Modes are those properties of a substance that can change while the substance remains the same thing. Attributes of substances, on the other hand, always remain unmodified and are constant.17

The relationship between modes and attributes can be elaborated using Descartes’ discussion of wax from the Second Meditation (AT VII 30–33/CSM II 20–22). Descartes considers that a piece of wax, when heated, can be molded into many shapes, for example, a cube, or a sphere. Each of these features of the piece of wax is a mode of the wax (that is, when the wax is molded into one of those shapes, say a cube, being cube is a mode of the wax). A piece of wax can undergo a change from being a cube to being a sphere and remain the same piece of wax. Shape in general, however, is an attribute of a piece of wax. Any piece of wax, so long as it exists, will have shape. As has been noted by other scholars, it is helpful to think of attributes and modes in terms of the determinable-determinate relationship. One can think of the attribute, shape in this case, as a determinable with any particular shape, or mode, as a determinate of the determinable (Nolan 1997a; Ott 2009: 44–49).18 All pieces of wax possess the determinable shape, which at any given time exist as some determinate shape.

In the Principles Descartes discusses the relationship between substances and principal attributes.19 Descartes explains: ‘To each substance there belongs one principal attribute; in the case of mind, this is thought, and in the case of body it is extension. A substance may indeed be known through any attribute at all; but each substance has one principal property which constitutes its nature and essence, and to which all its other properties are referred’ (AT VIIIa 25/CSM I 210–11). In this passage Descartes claims that each substance has one principal attribute.20 Principal attributes have two central features. First, the principal attribute constitutes the nature and essence of the substance. Descartes identifies the principal attribute of bodies as extension and the principal attribute of minds as thought. In the case of bodies, their essence and nature is extension or being extended. In the case of minds, their essence and nature is thought or thinking. Second, all modes (and other attributes) of a substance presuppose that substance’s principal attribute. For example, all the modes of the mind presuppose thought. That is, all the modes of the mind, doubting for example, can only exist in a thinking thing. In fact, all of the modes of the mind just are ways of thinking. Similarly, all the modes of body presuppose extension and just are ways of being extended. Having a shape presupposes being extended. So, all modes and attributes of a substance depend on that substance’s principal attribute.

Later in the Principles Descartes develops his conception of the principal attribute of a substance: ‘Thought and extension can be regarded as constituting the natures of intelligent substance and corporeal substance; they must then be considered as nothing else but thinking substance itself and extended substance itself—that is, as mind and body’ (AT VIIIa 30–31/CSM I 215). After describing the essence or nature of bodies as being extended and the essence or nature of a mind as thinking, Descartes identifies the nature of a thinking substance with the thinking substance itself and the nature of extended substance as extended substance itself. That is, a body just is its extension, while a mind just is its thought.21 Since the principal attribute constitutes the nature of a substance, the principal attribute just is the substance.22

With this background in hand, we can return to Elisabeth’s objections. In passage 1, she asks Descartes for a ‘more precise definition of the soul’ than the one Descartes offers in the Meditations, specifically, ‘of its substance separate from its action, that is, from thought.’23 Elisabeth continues ‘even if [encore que] we were to suppose them inseparable,’ we can by considering them apart ‘acquire a more perfect idea of them.’24 Here Elisabeth signals a disagreement with Descartes’ considered position that a substance and its principal attribute are identical. Elisabeth is asking for an account of what a soul is that is not simply an account of its action. She seems here to be challenging some aspect of the principal attribute component of Descartes’ dualism. One might worry about interpreting Elisabeth as questioning this component of Descartes’ dualism since it is only implicit in the Meditations and becomes explicit in the Principles. However, given the phrasing of the question, Elisabeth might be read as expecting that Descartes would offer an answer. That is, Elisabeth does not seem to be objecting per se, but asking for an elaboration on Descartes’ view.

Elisabeth offers two examples to illustrate the principal attribute problem: the mother’s womb and deep faints. I shall begin with the latter. Elisabeth suggests that it is hard to show that the soul and its action are inseparable because of deep faints. In deep faints it seems that thought ceases altogether. Indeed, we can consider such cases an extension and augmentation of the vapors problem. Instead of the physical cause (e.g., blood loss) simply undermining our custom of reasoning well, it undermines thinking and the capacity for thought altogether. Similarly, Elisabeth suggests that a fetus in the mother’s womb has a soul without thought. This is a second instance where thought and the soul may be separated.

Elisabeth’s worry is that in deep faints and in the womb, it is difficult to claim that the soul and thinking are inseparable, let alone identical. There are a number of aspects of the principal attribute component that Elisabeth may be questioning or at least that are subject to her objection. Her primary worry, I think, is that the soul and its thought are separable. If a soul and its thought are separable, then a soul cannot be identical to its thought. This is the part of the principal attribute component that Elisabeth is most clearly questioning. Several other aspects of Descartes’ account here might be similarly at issue, for example, whether substances in general have principal attributes, or whether substances in general are identical to principal attributes, but I take the key claim to simply be that in the case of our souls, souls and their activity of thinking are not identical.

While the principal attribute problem is offered quite briefly and in passing, it is I think quite significant and merits both attention and being distinguished from the other objections, especially the causal interface problem. The principal attribute problem is raised in her initial inquiry and is directly related to her main question to Descartes: to offer a more precise definition of the soul. It suggests, I believe, that Elisabeth’s main worry is about Descartes’ conception of soul and not mind-body interaction itself. And, the principal attribute problem is distinct from the causal interface problem. Elisabeth does not raise the principal attribute problem to illuminate the causal interface problem, but to offer more weight to her request for a better account of the soul. With the principal attribute problem, Elisabeth suggests a position that Descartes’ picture cannot accommodate. As discussed above, Descartes holds that a substance and its principal attribute are identical; Descartes identifies soul with thought. Elisabeth’s inquiry here suggests that she does not adopt this aspect of Descartes’ ontology. While Elisabeth does not elaborate much on what her view might be, she offers us enough to see that she is not (or would not be) satisfied with Descartes’ picture according to which a substance and its action (or in terminology from the Principles, a substance and its principal attribute) are identical.25 Elisabeth is questioning, and on my view rejecting, the principal attribute component of Descartes’ dualism.

In this paper, I have argued that Elisabeth offers three distinct objections to Descartes in these early letters: the causal interface problem, the vapors problem, and the principal attribute problem. These three objections are best read as criticisms primarily directed at Descartes’ account of the nature of the soul. While I am not unsympathetic to the suggestion, made by Margaret Atherton (2007) for example, that the texts from Elisabeth are not sufficient to allow us to make a definitive judgment about Elisabeth’s considered view of the soul, I do think we are in a position to articulate an interesting account of the soul that is at least suggested by her remarks.

One line of interpretation treats Elisabeth as a materialist or quasi-materialist about the soul.26 Other scholars have suggested that Elisabeth holds a dualist position, though not necessarily Descartes’ version of dualism.27 While there is much nuance in many of these discussions, the arguments in this paper broadly support the latter position according to which Elisabeth is embracing an ontological dualism of soul and body in terms of the real distinction component, but a distinctly non-Cartesian dualism in other ways.

None of the three distinct objections Elisabeth offers to Descartes are directed at the real distinction component. She agrees with Descartes on the soul and the body being different substances that can subsist apart. She parts ways with Descartes, or at least questions, the other three components of Descartes’ dualism outlined in section I: the principal attribute component, the differing natures component and the property-type component. She offers the vapors problem in the second letter, and this problem is designed to question the differing natures component and the property-type component of Descartes’ dualism (and by extension the principal attribute component). There are certain phenomena, Elisabeth contends, including instances where the soul loses the ability to reason well on account of a physical cause, that cannot be explained without modifying our understanding of the soul to allow for at least extended properties. The principal attribute problem, based on cases where it is plausible that a soul and its action come apart, give us more reason to doubt the principal attribute component of Descartes’ dualism. Finally, the causal interface problem is used to question the property-type component, not least to suggest that the soul has some unknown properties over and above purely thinking modes.

In fact, in passage 4, Elisabeth tells Descartes that ‘I think there are some properties of the soul’ that are unknown to us that could overturn what the Meditations persuaded her of ‘by such good reasoning,’ namely, ‘the nonextendedness of the soul’ (AT IV 2/S 72).28 In passage 5, Elisabeth explains:

As I read this passage, Elisabeth is in a sense granting Descartes the real distinction argument. Elisabeth is acknowledging that Descartes has shown that it is possible that souls exist as substances with only incorporeal properties, and that bodies exist as extended things and even that mind-body unities along Descartes’ lines are metaphysically possible. What she is denying, based on experiences of actual mental phenomena, is that our souls are purely incorporeal things. Rather, based on her experiences, we must attribute heretofore unknown and material properties to the soul. To take our souls to be purely incorporeal is to form an erroneous judgment going beyond what we perceive. What Descartes has shown, in a sense, is that there could be purely incorporeal souls, or even that we could be purely incorporeal souls, but not that we are purely incorporeal souls. Rather, our actual experience shows us that we must also have some physical properties or aspects in the soul.29

All told, Elisabeth suggests that there is empirical and phenomenal evidence that there is more to our soul than Descartes allows. She offers three distinct problems for Descartes’ account, all specifically directed at Descartes’ conception of the nature of the soul: the causal interface problem, the vapors problem, and the principal attribute problem. The three of these combined give us strong reason to doubt that the soul is pure thought. Instead, they suggest that the soul in fact has some physical properties. As Elisabeth tells us, it is hard to believe that a soul, having nothing in common with body, could be so governed by it.