Would you call Plato's philosophy of mind 'dualist'?
If so, in what sense?


Philosophy of mind is the subset of philosophical enquiry that explores the nature of the mind, and addresses such questions as "what are (are there) mental events?", "what are the mental functions?", "what are mental properties?", "what is consciousness?"and (of particular interest to this essay) "what is the relationship between the mental and the physical body?"The relationship between the mind and the body (the so-called "mind-body problem"), is commonly seen as the central issue in the philosophy of mind.

Dualism and monism are the two major schools of thought that attempt to resolve this mind-body problem.   Dualism is a set of views which begins with the claim that mental phenomena are, in some critical respects, non-physical.   (The body, in this context, is universally viewed as physical.)   A philosophy of mind dualist, therefore, maintains that mind and body are in some categorical way separate from each other.   The monist denies this.   Rene Descartes is perhaps the most famous of the modern mind-body dualists.   Daniel Dennett is perhaps the most famous of the modern monists.

The essay title first raises the question of whether Plato's conception of the relationship between mind and body should best be classified on the "dualist"side, or on the "monist"side of this bifurcation of the field.   I think that Plato is clearly a Dualist.   The second question raised by the essay title is which particular flavour of dualism would best characterize Plato's philosophy of mind.   I think it is equally clear that Plato should best be described as a "substance dualist", and as such a predecessor of Descartes.   In this essay, I will try to support both conclusions.

In the Philosophy of Mind, the modern concept of "mind"is equivalent, for all intents and purposes, to the ancient Greek notion of "soul".   ("Psyche" -- the ancient Greek goddess of the soul.   Probably coming from the Greek "psychein" -- "to breath").   This was the ancient Greek term used to distinguish between things that are alive and things that are not.   Things alive had "psyche".   Things dead did not.   It was the soul that allowed one to feel, think, possess knowledge, and choose rightly.   As early as the Iliad, the soul (psyche) resided in the body, and left it upon death.   In the popular culture of ancient Greece, a presumption of body-soul duality was the norm.   It was also, however, a cultural norm that the soul was created at birth, and dissolved when it left the body at death.   Plato's arguments for the immortality of the soul (in the Phaedo) introduced what was at the time a relatively uncommon conception of the soul.

The earliest known systematic (philosophical) description of body and soul duality is found in Plato's Phaedo dialogue.   It is here that Plato first formulated his famous Theory of Forms as distinct and immaterial substances of which the objects and other phenomena that we perceive in the world are nothing more than mere shadows -- imperfect reflections or copies or resemblances.   Plato's body-soul dualism becomes obvious in one of the four arguments (approximately, depending on how the reasoning is divided) that Plato offers in the Phaedo to "prove"that the soul is immortal.

In the argument from Forms, Plato reasons:-

a)   The Forms are uniform, independent, constant, invariable, invisible, immortal, uncreated, indivisible [unsupported premise]

b)   Particulars are variable, dependent on the Forms, inconstant, visible, created, and dissoluble.

c)   The body is variable (ages), inconstant (changes with health), visible (obviously), created (born), and dissoluble (dies and decays to dust).

d)   The body is therefore a particular.

e)   The soul is uniform, independent, constant, invariable, and invisible [a then culturally popular characterization of the psyche].

f)    The soul is therefore not a particular.

g)   The soul is (or "is akin to", or "is similar to") a Form [invalid conclusion -- fallacy of the undistributed middle].

h)   The soul is immortal, uncreated, indivisible.

Here, Socrates draws upon the presumed resemblance between a Form and the Soul.   He is also, of course, making a clear assertion of body-soul duality -- the body and the soul are assumed to have distinctly different properties.   He then argues that the soul therefore necessarily must possess the all the other presumed properties of a Form rather than any of the properties of a particular.   He is arguing that because it is popularly accepted that the soul possesses some of the properties he attributes to Forms, it therefore must possess all the other properties that he attributes to Forms.   To quote a significant passage "If the objects exist which are always on our lips, the beautiful and the good and all reality of that kind, it follows that as surely as those objects exist so surely our souls exist before we are born"(Phaedo 76d).

It is irrelevant for the purposes of this essay, of course, that the reasoning of this argument is logically fallacious, or that the entire structure of reasoning crumbles to naught if one fails to accept any of Plato's critical and unchallenged premises -- the recollection theory of knowledge; the theory of forms; the properties of forms; and the properties of souls.

With his description of Forms, Plato makes it clear that the Forms are not physically existing entities.   They are the eternal "Perfect Ideals"of which physically existing entities are but imperfect copies.   He also makes it clear that he regards the Forms as we would regard universal, general, categorical concepts or ideas.   Moreover, from the way in which he uses the Forms to "prove"the immortality of the soul, it is evident that he sees these Forms as having actual existence in some "other"realm distinct from the world around us.   In both the Phaedo and the Meno, he argues we do not learn about the Forms in this world, but merely "recollect"the Forms from an earlier encounter between the soul and the Forms in the realm of Forms.   It is irrelevant to this essay just how "akin"or "similar"to Forms the soul is considered by Plato.   It is sufficient that he attributes to the soul all of the properties that he attributes to Forms.   It is thus clear from the text of the Phaedo that Plato conceives of the soul as something distinctly different from the body, and surviving beyond the body (immortal).  

Based on this evidence from the Phaedo, supported by the historical evidence we have of the then popular cultural beliefs about body-soul duality, the conclusion is inescapable that Plato can only be described as a dualist.   In his dialogues Plato establishes the paradigm philosophical characterization of mind-body dualism.

However, over the two millennia since Plato, within the modern complexity of the philosophy of mind, mind-body dualism has taken on more baggage than the simple characterization offered by Plato.   Modern mind-body dualism makes assertions about the nature of mind and body existence that can be very roughly divided into three different types:

(1) "Substance"dualism is most famously defined by Rene Descartes.   It maintains that there exist two fundamental kinds of substance: mental and material.   Mental substance does not have extension in space.   Material substance does not think.  

(2) "Property"dualism (sometimes referred to as "emergent"dualism) maintains that when matter is organized in an appropriate way (the way human bodies are organized), mental properties emerge.   Property dualists maintain that while there is only one fundamental substance -- the material, there exist two distinct kinds of properties: the physical and the mental.   They maintain that mental properties (by stipulation non-physical) exist in some physical substances (specifically brains).   Mental events, functions, phenomena are emergent and supervene on the material.   It is often difficult to distinguish a property dualist from a monist, since both maintain that there is but a single underlying substance.   However, property dualism can be distinguished by the core belief that things mental (mental properties) ultimately cannot be adequately described at the physical level using just physical properties.   Things mental are "irreducible"to the physical.   John Searle is perhaps the best known of modern property dualists.

(3) "Predicate"dualism maintains that while there is only one substance (the material) and one set of properties of substances (the physical), the language that we use to describe mental events cannot be translated into (reduced to) the language of physical events.   Unlike the property dualist, the predicate dualist maintains that the distinction between what we describe as mental and what we describe as physical comes down to linguisitic convention -- things mental we describe using functional terms, not the natural kind terms that we use for properties.   So, as with property dualism, things mental (mental functions) ultimately cannot be adequately described using just physical properties.   Jerry Fodor is perhaps the best known of the predicate dualists.

Based on the evidence I have presented above from the Phaedo, I think one can safely conclude that Plato considers the individual person to consist of two distinctly different parts -- body and soul.   He explicitly says that a person is a body with an entrapped soul that yearns to be free.   Each part has it own set of properties, its own set of functions, and its own realm of existence Admittedly, we have to "read between the lines"and presume that Plato envisages a different substance for each realm.   And given Plato's treatment of forms as the "true perfect ideal"while physical world particulars are but "imperfect shadows", one might debate as to what extent Plato regards the world of particulars as a "real"world.   But it is undeniable that he considers the body to exist in a world that is separate from that of the Forms and the un-embodied soul.   In terms of the modern divisions of mind-body dualism, one would therefore have to characterize Plato as a Substance Dualist.

It is worth noting, however, that Plato arrives at his substance dualism from a completely different direction than does Descartes.   A sufficiently different direction that some might question whether the two should be classed together.   Plato comes to his substance dualism from a metaphysical / ontological basis -- it is an unquestioned premise to Plato that body and soul exist as separate and different entities.   There is no question, anywhere in his writing, of trying to demonstrate or support this basic ontological premise.   Plato's concern is to investigate and describe the properties of the soul.   Descartes, on the other hand, reasons himself into substance dualism by starting with epistemology.   Employing his famous "method of doubt", Descartes reasons that everything that he believes exists (his metaphysics) may be the artificial creation of some evil demon intent on deceiving him.   The only thing about which Descartes claims to be certain (to "know") is that he is and he thinks.   Therefore, he concludes, everything physical is dubitable while things mental are obviously indubitable.   So the physical must be different from the mental.   Hence body-soul dualism.   However different their starting points, they do both maintain that the body and the soul/mind are categorically different substances.   And that is substance dualism.

Once it is granted (or assumed) that body and soul are fundamentally different substances, then three additional classifications can be brought to bear to further refine the dualist conception.   Depending on just how one views the causal relationship between the two substances involved, substance dualism can be further categorized as -

(a) Interactionism   -   the belief that body and soul (or mental events and physical events) causally influence each other.   This is undeniably one of our common-sense beliefs, because it appears to be a feature of everyday experience.   The world causes our experiences, and we react with beliefs and thoughts to those experiences.   Our thoughts cause our speech and our behaviours. There is, therefore, a massive natural prejudice in favour of interactionism.   In the absence of argument to the contrary, one would have to assume interactionism as the default.

(b) Epiphenomenalism   -   the belief that mental events are caused by physical events, but have in turn no causal influence on the physical.   Things mental supervene on the physical.   Body and soul may be separate, but the events in the soul are reflections (or descriptions) of things physical, and cannot cause anything.   Epiphenomenalism maintains the coherence of the physical sciences, while also maintaining that there are separate mental phenomena that do exist in their own right.

(c) Parallelism   -   a belief that preserves both the physical and mental realms intact, but denies all causal interaction between them.   The mental and physical run in parallel synchrony with each other, but only because they are/were designed to operate that way, not because they have any influence on each other.   Parallelism has tended to be adopted only by those who maintain that the synchrony is maintained by God.   (Leibniz is perhaps the best example.)

Although these subcategories of dualism did not exist at the time, Descartes very clearly can be classed as an Interactionist.   He maintained that there is interaction between body and soul, and suggested that it may take place within the penal gland.   As for Plato, there is little in the works of Plato that can be clearly interpreted as placing him in any of the three subcategories.   The "problem"of mind-brain interaction is a modern one resutling from advances in physics and medicine.   In Plato's time, it was not an issue.   Popular culture was familiar with (comfortable with) the notion of non-material Gods influencing the material world.   The question of how a non-material mind influences a material body would have been a non-issue.   The best we can do, then, is draw upon the common sense natural prejudice and place Plato along with Rene Descartes, in the category of Interactionist Mind-Body Dualists.

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