I wrote this essay for my early modern philosophy course this term. It was a challenge to write because of how fundamental the argument is about the human person and what we can know. I am happy I made it to this stage, but I see it as a work in progress. I have learned a lot about hylomorphism and cartesian dualism, but I feel I still have a lot to learn about the two, and wish I understood more clearly why hylomorphism may be more accurate.

Before the essay, first a few thoughts from later on in the writing process:

• A thinker, I think it is Pierre-Sylvain Régis, proposed an additional reason for why the mind is necessarily linked to the body -- that because we think slowly and not immediately, thought must be in time, which must be in space, and therefore has a component that is necessarily “extended”. This is an interesting arguement I’d like to dive into more deeply, but I just learned of it this afternoon so I wasn’t able to incorporate it into this version.

• Also, if thought is physical, or necessarily has a physical component, then the problem of definitions goes back to the Cogito. The “ego” would then denote the an extended substance -- perhaps a body -- or at least whatever is needed for the act of thinking to occur.

Aight, here is the current version of the essay:

     During the early 1600s, in a time when there came a sudden questioning of long-held beliefs about the fundamental makeup of the natural world, Descartes wrote The Meditations, following the journey of a person doubting previous assumptions and building back up as certain as possible. As he builds up from his Archemedian point – the existence of his mind – he concludes that the body is something distinct from the mind. This comes to be known as mind-body dualism. This conclusion is different from the Aristotelian understanding of the human body / psyche relation in that the latter sees both the body and psyche as necessary to make up a human person with the psyche actualizing the potentiality of the body. This relation is often called hylomorphism. Hylomorphism provides a more accurate understanding of the human person than Descartes’ dualism because his reasoning for why the mind and body are “distinct” from one another falls short of his own principle and also because humans experience themselves as a single unity, rather than a combination of mind and body.

Descartes’ project in his Meditations is to see what he can be certain of. He comes to the Archimedean point, “I am, I exist”. This is the first and most fundamental thing he is certain of. He is certain of it because he knows something is doubting his own existence, and in this doubting, there must be something there. This is the only conclusion he can yet take at this level of certainty. Descartes is not yet able to make a judgment about whether his imagination or body or the outer world exists. He concludes, “Thought exists; it alone cannot be separated from me.” (Meditations, p44) Because he is able to wrap his arms around this point only, even when he supposes that all else is nothing, he concludes he is “precisely nothing but a thinking thing; that is, a mind, or intellect, or understanding, or reason.” (Meditations, p44)

As he moves on, Descartes characterizes the body as a “sort of mechanism” outfitted with various parts. (Meditations, p66) Unlike the mind, the body is a nonthinking thing, characterized by the fact that it is “extended”, or has “length, breadth and depth”. (Meditations, p58)

This understanding, where there is both a body that is spatially extended, and a mind which has the property of “thinking”, is known as Cartesian Dualism, more broadly known as substance dualism.

Descartes reasons that the mind and the body are distinct from one another because they qualify as “clear and distinct”. In Meditation Six, he writes, “on the one hand I have a clear and distinct idea of myself, insofar 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. And accordingly, it is certain that I am really distinct from my body, and can exist without it.” (Meditations, p64) This conclusion pivots on Descartes’ understanding of “clear and distinct” ideas. An idea is clear when it is seen fully and well with the intellect (as opposed to just the imagination), and distinct when all other ideas not belonging to it are completely excluded from it. (Descartes, Principles of Philosophy PI, S45) Because of Descartes’ definition of mind as a thinking, non-extended thing and a body as an extended, non-thinking thing, they are definitionally distinct according to the “clear and distinct” principle. Following from this, the two are able to exist alone without the other.

Later in Meditation Six, Descartes provides another argument in support of this distinction. He argues, “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. For when I consider the mind, or myself in so far as I am merely a thinking thing, I am unable to distinguish any parts within myself; I understand myself to be something quite single and complete….By contrast, there is no corporeal or extended thing that I can think of which in my thought I cannot easily divide into parts; and this very fact makes me understand that it is divisible. This one argument would be enough to show me that the mind is completely different from the body” (Meditation, p67) This rests again, however, on the definitions of the natures of mind and body. A body is divisible definitionally in that is extended in length, breadth and depth, whereas a mind is not extended, and therefore unable to be divided.

While Descartes set off to see what he was certain of, he came away with a different fundamental understanding of the relation of mind and body to what had been generally held previously: an explanation of the person according to hylomorphism.

Aristotle was the first to propose hylomorphism in order to provide a framework to explain how change can happen and yet how there is something that persists through the change. Hylomorphism posits that ordinary objects are compounds of form and matter. (Aristotle, De Anima, B2.1) Form actualizes matter; matter is potentiality. There is an interrelationship between form and matter: form is “what makes some matter which is potentially F actually F”, and matter is “that which persists” in a change, and is at one point potentiality. (SEP Aristotle, 8) For example, when a sculptor is going to make a statue out of a lump of copper, the copper is potentially a statue, and when it is informed with the form of statue it is a statue. The copper persists throughout, though it acquires a new form.

The human person is the compound of psyche (similar to mind) and body: the psyche actualizes the potentiality of the body. (Aristotle, De Anima, B2.1) Without both the psyche and the matter, there is no human. Some forms of a thing are essential and make up its substantial form, or essence. The psyche is not separable from the body for the matter to be the same thing. Rather, when the psyche actualizes the body, a human comes into being. (Aristotle, De Anima, B2.1) Aristotle notes that with this conception of mind and body, it is meaningless to ask whether the mind and body are one just as it is meaningless to ask “whether the wax and the shape given to it by the stamp are one, or generally the matter of a thing and that of which it is the matter.” (Aristotle, De Anima, B2.1)

Descartes has two main flaws with his conception of the mind and body as separate, both of which hylomorphism accounts for.

The first is that Descartes relies on the principle of “clear and distinct ideas” as grounds for why the mind can exist without a body, but his reasoning for why the mind and body are distinct falls short. Under Descartes’ criteria, for two things to be distinct, they must be “so sharply separated from all other perceptions that every part of it is [clear].” (Descartes, Principles of Philosophy PI, S45)

But physical extension is not so sharply separable from that of the activity of thinking. For, when we think, there are corresponding physical movements in our brains. If you take away the brain, it is unclear whether thought can occur. It seems that thoughts themselves have a physical component – physical movements within the mind – and can only occur when there is this material potentiality present.

If a person attempts to intellect “thinking”, or to intellect a mind thinking, this appears to be an impossible task, for thoughts themselves seem to be extended substances, and one cannot just intellect an extended substance. This person would be imagining the thought, not simply intellecting it. And imagination is part of the body, so it requires a body to imagine it.

It is worth noting that this objection does not disprove Descartes’ argument outright by showing that thought is necessarily physical. For while it appears likely that thoughts have a physical component to them, it is unclear whether it can be said that they most certainly are physical or not. With scientific tools, researchers are able to see physical movements within the brain according to when and what a person thinks. (Brain Scans, Yale Medicine Magazine) Whether these movements are necessary or not to the act of thinking itself is uncertain.

But this objection does provide enough reason to say that Descartes cannot say that the mind is certainly “distinct” from the body, for this would require that thought and the physical would be “so sharply separated from all other perceptions that every part of it is [clear]”, and this is not the case as described above. (Descartes, Principles of Philosophy PI, S45) Therefore, with the distinct principle negated, Descartes does not have sufficient grounds to say that the mind and the body are “clear and distinct”, and therefore is left without a solid argument for their being separated from one another.

Additionally, when the “distinct” part of the “clear and distinct principle” breaks down, so does his argument that they are separate because of divisibility. For Descartes compares the thinking of the mind with extended objects like the body, and contends that the body can be divided but the mind cannot be. But if the mind and the body are not necessarily separable from one another, he cannot put them opposite one another and say that the one can be divided while the other cannot be. For the dividing of the one could come at the cost of the ability for the other to be exercised at all.

For example, if parts of the body were divided, and a person lost their arms, legs, even their chest and skull, and their brain was being supported by a special machine that kept it as if it were in the skull, then the matter itself has been divided, and the mind is not divided. But if the brain is severed in half, or further into tiny bits, the mind no longer has anything to think with. The thoughts are not able to be had because the matter necessary to think is not present as it may need to be. So while the mind is experienced as indivisible, it cannot necessarily exercise its essence – that is thinking – without enough of the appropriate extended body to do such.

Hylomorphism, on the other hand, does not necessitate the mind and the body to be “distinct” from one another, so it does not rest on this quality of being “distinct”. With the hylomorphic conception of the human person, a person is realized when form (the psyche) has actualized matter (the body). A second problem with Cartesian dualism is that its definitions of the nature of mind and body as necessarily distinct from one another is not reflected by the experience of the human person. If the human was actually made fundamentally up of two parts – a thinking part and a body part – this would be reflected in one’s experience: a mind part and a body part. But this is not how humans experience their bodies, and it is not how we refer to ourselves. When I am playing basketball and I shoot a free throw, it is I who threw the free throw. Arms do not shoot free throws, people shoot free throws. Of course both are true, but our intuition does not distinguish between our mind and body when we conceive of ourselves. We experience ourselves as a whole, not two radically different parts.

Hylomorphism accounts for this unity. We experience life in this union, not so much as two parts of ourselves. Hylomorphism proposes a union of form and matter, of psyche and body, and we see ourselves as such – with extended substance and thought, but the two are not fundamentally separate. In the Summa Theologica, Aquinas speaks to this point, that, “neither the eye nor the hand can be said to subsist through itself; nor can either for that reason be said to operate through itself. Hence, the operation of the parts is attributed to the whole through each part. For we say that a human being sees with the eye, and feels with the hand, and not in the same sense as when we say that what is hot gives heat by its heat. For heat, strictly speaking, does not give heat. We may therefore say that the soul understands, as the eye sees, but it is more correct to say that a human being understands through the soul.” (Aquinas, ST, I, Q. 75, A. 2, Ad. 2)

Thus, because the “distinct” part of the “clear and distinct principle” does not hold up, and because humans experience life as a unity as opposed to two separate parts, hylomorphism provides a more accurate conception of the human person.

One potential objection to the latter part of this argument, that of human experience, is that Descartes acknowledges this experience of the human person as a unity, saying, “nature also teaches that I am present to my body not merely in the way a sailor is present in a ship, but that I am most tightly joined and, so to speak, commingled with it, so much so that I and the body constitute one single thing”. (Meditations, p65) This claim is surprising, because while it is indeed reflected in human experience, just previous to this in the Meditations because it is seemingly contrary to what the mind and the body are essentially. According to Descartes, the mind is essentially a thinking, non-extended thing, and the body is essentially a non-thinking, extended thing. If a person is, at their core, just their mind and not their body, then his claim that the two are experienced as a unity is a stretch to say the least because of how fundamentally different the two are.

Hylomorphism, on the other hand, proposes a union between the mind and the body. The two are not opposites, but rather, the mind actualizes the body, and only when the two are together is there a human person. Because individuals experience themselves as a unity, as stated above in the “free throw” example, this position is far more likely to reflect this experience. Just because Descartes acknowledges that his conception of mind and body are experienced like this, doesn’t make it more likely that they are experienced as such, particularly when he does not give any reason for why this may be possible, and the hylomorphic conception proposes a unity in the first place.

Bibliography

Descartes, René. “Meditations on First Philosophy.”Modern Philosophy: An Anthology of Primary Sources, edited by Roger Ariew and Eric Watkins, Hackett Publishing, 2019, 44-67. Descartes, Rene. “Selections of The Principles of Philosophy”, edited by Steve Harris, Charles Franks, blackmask.com. Aristotle. “De Anima (on the Soul).” De Anima Excerpts, https://faculty.uca.edu/rnovy/Aristotle--De Anima excerpts.htm. Shields, Christopher, "Aristotle", The Stanford Encyclopedia of Philosophy (Spring 2022 Edition), Edward N. Zalta (ed.), https://plato.stanford.edu/archives/spr2022/entries/aristotle/. “Can Brain Scans Reveal How We Think?” Medicine.yale.edu, medicine.yale.edu/news/yale-medicine-magazine/article/can-brain-scans-reveal-how-we-think1/. Aquinas, Thomas. “SUMMA THEOLOGIAE: Man Who Is Composed of a Spiritual and a Corporeal Substance: And in the First Place, Concerning What Belongs to the Essence of the Soul (Prima Pars, Q. 75).” www.newadvent.org, www.newadvent.org/summa/1075.htm.

I wrote this essay for my early modern philosophy course this term. It was a challenge to write because of how fundamental the argument is about the human person and what we can know. I am happy I made it to this stage, but I see it as a work in progress. I have learned a lot about hylomorphism and cartesian dualism, but I feel I still have a lot to learn about the two, and wish I understood more clearly why hylomorphism may be more accurate.

Before the essay, first a few thoughts from later on in the writing process:

• A thinker, I think it is Pierre-Sylvain Régis, proposed an additional reason for why the mind is necessarily linked to the body -- that because we think slowly and not immediately, thought must be in time, which must be in space, and therefore has a component that is necessarily “extended”. This is an interesting arguement I’d like to dive into more deeply, but I just learned of it this afternoon so I wasn’t able to incorporate it into this version.

• Also, if thought is physical, or necessarily has a physical component, then the problem of definitions goes back to the Cogito. The “ego” would then denote the an extended substance -- perhaps a body -- or at least whatever is needed for the act of thinking to occur.

Aight, here is the current version of the essay:

     During the early 1600s, in a time when there came a sudden questioning of long-held beliefs about the fundamental makeup of the natural world, Descartes wrote The Meditations, following the journey of a person doubting previous assumptions and building back up as certain as possible. As he builds up from his Archemedian point – the existence of his mind – he concludes that the body is something distinct from the mind. This comes to be known as mind-body dualism. This conclusion is different from the Aristotelian understanding of the human body / psyche relation in that the latter sees both the body and psyche as necessary to make up a human person with the psyche actualizing the potentiality of the body. This relation is often called hylomorphism. Hylomorphism provides a more accurate understanding of the human person than Descartes’ dualism because his reasoning for why the mind and body are “distinct” from one another falls short of his own principle and also because humans experience themselves as a single unity, rather than a combination of mind and body.

Descartes’ project in his Meditations is to see what he can be certain of. He comes to the Archimedean point, “I am, I exist”. This is the first and most fundamental thing he is certain of. He is certain of it because he knows something is doubting his own existence, and in this doubting, there must be something there. This is the only conclusion he can yet take at this level of certainty. Descartes is not yet able to make a judgment about whether his imagination or body or the outer world exists. He concludes, “Thought exists; it alone cannot be separated from me.” (Meditations, p44) Because he is able to wrap his arms around this point only, even when he supposes that all else is nothing, he concludes he is “precisely nothing but a thinking thing; that is, a mind, or intellect, or understanding, or reason.” (Meditations, p44)

As he moves on, Descartes characterizes the body as a “sort of mechanism” outfitted with various parts. (Meditations, p66) Unlike the mind, the body is a nonthinking thing, characterized by the fact that it is “extended”, or has “length, breadth and depth”. (Meditations, p58)

This understanding, where there is both a body that is spatially extended, and a mind which has the property of “thinking”, is known as Cartesian Dualism, more broadly known as substance dualism.

Descartes reasons that the mind and the body are distinct from one another because they qualify as “clear and distinct”. In Meditation Six, he writes, “on the one hand I have a clear and distinct idea of myself, insofar 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. And accordingly, it is certain that I am really distinct from my body, and can exist without it.” (Meditations, p64) This conclusion pivots on Descartes’ understanding of “clear and distinct” ideas. An idea is clear when it is seen fully and well with the intellect (as opposed to just the imagination), and distinct when all other ideas not belonging to it are completely excluded from it. (Descartes, Principles of Philosophy PI, S45) Because of Descartes’ definition of mind as a thinking, non-extended thing and a body as an extended, non-thinking thing, they are definitionally distinct according to the “clear and distinct” principle. Following from this, the two are able to exist alone without the other.

Later in Meditation Six, Descartes provides another argument in support of this distinction. He argues, “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. For when I consider the mind, or myself in so far as I am merely a thinking thing, I am unable to distinguish any parts within myself; I understand myself to be something quite single and complete….By contrast, there is no corporeal or extended thing that I can think of which in my thought I cannot easily divide into parts; and this very fact makes me understand that it is divisible. This one argument would be enough to show me that the mind is completely different from the body” (Meditation, p67) This rests again, however, on the definitions of the natures of mind and body. A body is divisible definitionally in that is extended in length, breadth and depth, whereas a mind is not extended, and therefore unable to be divided.

While Descartes set off to see what he was certain of, he came away with a different fundamental understanding of the relation of mind and body to what had been generally held previously: an explanation of the person according to hylomorphism.

Aristotle was the first to propose hylomorphism in order to provide a framework to explain how change can happen and yet how there is something that persists through the change. Hylomorphism posits that ordinary objects are compounds of form and matter. (Aristotle, De Anima, B2.1) Form actualizes matter; matter is potentiality. There is an interrelationship between form and matter: form is “what makes some matter which is potentially F actually F”, and matter is “that which persists” in a change, and is at one point potentiality. (SEP Aristotle, 8) For example, when a sculptor is going to make a statue out of a lump of copper, the copper is potentially a statue, and when it is informed with the form of statue it is a statue. The copper persists throughout, though it acquires a new form.

The human person is the compound of psyche (similar to mind) and body: the psyche actualizes the potentiality of the body. (Aristotle, De Anima, B2.1) Without both the psyche and the matter, there is no human. Some forms of a thing are essential and make up its substantial form, or essence. The psyche is not separable from the body for the matter to be the same thing. Rather, when the psyche actualizes the body, a human comes into being. (Aristotle, De Anima, B2.1) Aristotle notes that with this conception of mind and body, it is meaningless to ask whether the mind and body are one just as it is meaningless to ask “whether the wax and the shape given to it by the stamp are one, or generally the matter of a thing and that of which it is the matter.” (Aristotle, De Anima, B2.1)

Descartes has two main flaws with his conception of the mind and body as separate, both of which hylomorphism accounts for.

The first is that Descartes relies on the principle of “clear and distinct ideas” as grounds for why the mind can exist without a body, but his reasoning for why the mind and body are distinct falls short. Under Descartes’ criteria, for two things to be distinct, they must be “so sharply separated from all other perceptions that every part of it is [clear].” (Descartes, Principles of Philosophy PI, S45)

But physical extension is not so sharply separable from that of the activity of thinking. For, when we think, there are corresponding physical movements in our brains. If you take away the brain, it is unclear whether thought can occur. It seems that thoughts themselves have a physical component – physical movements within the mind – and can only occur when there is this material potentiality present.

If a person attempts to intellect “thinking”, or to intellect a mind thinking, this appears to be an impossible task, for thoughts themselves seem to be extended substances, and one cannot just intellect an extended substance. This person would be imagining the thought, not simply intellecting it. And imagination is part of the body, so it requires a body to imagine it.

It is worth noting that this objection does not disprove Descartes’ argument outright by showing that thought is necessarily physical. For while it appears likely that thoughts have a physical component to them, it is unclear whether it can be said that they most certainly are physical or not. With scientific tools, researchers are able to see physical movements within the brain according to when and what a person thinks. (Brain Scans, Yale Medicine Magazine) Whether these movements are necessary or not to the act of thinking itself is uncertain.

But this objection does provide enough reason to say that Descartes cannot say that the mind is certainly “distinct” from the body, for this would require that thought and the physical would be “so sharply separated from all other perceptions that every part of it is [clear]”, and this is not the case as described above. (Descartes, Principles of Philosophy PI, S45) Therefore, with the distinct principle negated, Descartes does not have sufficient grounds to say that the mind and the body are “clear and distinct”, and therefore is left without a solid argument for their being separated from one another.

Additionally, when the “distinct” part of the “clear and distinct principle” breaks down, so does his argument that they are separate because of divisibility. For Descartes compares the thinking of the mind with extended objects like the body, and contends that the body can be divided but the mind cannot be. But if the mind and the body are not necessarily separable from one another, he cannot put them opposite one another and say that the one can be divided while the other cannot be. For the dividing of the one could come at the cost of the ability for the other to be exercised at all.

For example, if parts of the body were divided, and a person lost their arms, legs, even their chest and skull, and their brain was being supported by a special machine that kept it as if it were in the skull, then the matter itself has been divided, and the mind is not divided. But if the brain is severed in half, or further into tiny bits, the mind no longer has anything to think with. The thoughts are not able to be had because the matter necessary to think is not present as it may need to be. So while the mind is experienced as indivisible, it cannot necessarily exercise its essence – that is thinking – without enough of the appropriate extended body to do such.

Hylomorphism, on the other hand, does not necessitate the mind and the body to be “distinct” from one another, so it does not rest on this quality of being “distinct”. With the hylomorphic conception of the human person, a person is realized when form (the psyche) has actualized matter (the body). A second problem with Cartesian dualism is that its definitions of the nature of mind and body as necessarily distinct from one another is not reflected by the experience of the human person. If the human was actually made fundamentally up of two parts – a thinking part and a body part – this would be reflected in one’s experience: a mind part and a body part. But this is not how humans experience their bodies, and it is not how we refer to ourselves. When I am playing basketball and I shoot a free throw, it is I who threw the free throw. Arms do not shoot free throws, people shoot free throws. Of course both are true, but our intuition does not distinguish between our mind and body when we conceive of ourselves. We experience ourselves as a whole, not two radically different parts.

Hylomorphism accounts for this unity. We experience life in this union, not so much as two parts of ourselves. Hylomorphism proposes a union of form and matter, of psyche and body, and we see ourselves as such – with extended substance and thought, but the two are not fundamentally separate. In the Summa Theologica, Aquinas speaks to this point, that, “neither the eye nor the hand can be said to subsist through itself; nor can either for that reason be said to operate through itself. Hence, the operation of the parts is attributed to the whole through each part. For we say that a human being sees with the eye, and feels with the hand, and not in the same sense as when we say that what is hot gives heat by its heat. For heat, strictly speaking, does not give heat. We may therefore say that the soul understands, as the eye sees, but it is more correct to say that a human being understands through the soul.” (Aquinas, ST, I, Q. 75, A. 2, Ad. 2)

Thus, because the “distinct” part of the “clear and distinct principle” does not hold up, and because humans experience life as a unity as opposed to two separate parts, hylomorphism provides a more accurate conception of the human person.

One potential objection to the latter part of this argument, that of human experience, is that Descartes acknowledges this experience of the human person as a unity, saying, “nature also teaches that I am present to my body not merely in the way a sailor is present in a ship, but that I am most tightly joined and, so to speak, commingled with it, so much so that I and the body constitute one single thing”. (Meditations, p65) This claim is surprising, because while it is indeed reflected in human experience, just previous to this in the Meditations because it is seemingly contrary to what the mind and the body are essentially. According to Descartes, the mind is essentially a thinking, non-extended thing, and the body is essentially a non-thinking, extended thing. If a person is, at their core, just their mind and not their body, then his claim that the two are experienced as a unity is a stretch to say the least because of how fundamentally different the two are.

Hylomorphism, on the other hand, proposes a union between the mind and the body. The two are not opposites, but rather, the mind actualizes the body, and only when the two are together is there a human person. Because individuals experience themselves as a unity, as stated above in the “free throw” example, this position is far more likely to reflect this experience. Just because Descartes acknowledges that his conception of mind and body are experienced like this, doesn’t make it more likely that they are experienced as such, particularly when he does not give any reason for why this may be possible, and the hylomorphic conception proposes a unity in the first place.

Bibliography

Descartes, René. “Meditations on First Philosophy.”Modern Philosophy: An Anthology of Primary Sources, edited by Roger Ariew and Eric Watkins, Hackett Publishing, 2019, 44-67. Descartes, Rene. “Selections of The Principles of Philosophy”, edited by Steve Harris, Charles Franks, blackmask.com. Aristotle. “De Anima (on the Soul).” De Anima Excerpts, https://faculty.uca.edu/rnovy/Aristotle--De Anima excerpts.htm. Shields, Christopher, "Aristotle", The Stanford Encyclopedia of Philosophy (Spring 2022 Edition), Edward N. Zalta (ed.), https://plato.stanford.edu/archives/spr2022/entries/aristotle/. “Can Brain Scans Reveal How We Think?” Medicine.yale.edu, medicine.yale.edu/news/yale-medicine-magazine/article/can-brain-scans-reveal-how-we-think1/. Aquinas, Thomas. “SUMMA THEOLOGIAE: Man Who Is Composed of a Spiritual and a Corporeal Substance: And in the First Place, Concerning What Belongs to the Essence of the Soul (Prima Pars, Q. 75).” www.newadvent.org, www.newadvent.org/summa/1075.htm.