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Mariah Harrod
Professor A. Roche
Philosophy 210
April 20, 2015
Spinoza’s Mind-Body Monism and its Connection to Materialism
Our perception of self as both an external body and an internal stream of consciousness—
a series of present moments and their subsequent descent into the past—led Descartes to assert
that the body and mind compose two distinct substances. In the process of accepting Descartes’
theory of mind-body dualism, later philosophers Leibniz and Malebranche also inherit the
obligation to explain whether and how two distinct substances interact. Whether their individual
expositions succeed is a matter we will not discuss too extensively, for their hypothetical
successes remain rooted in the misconception that consciousness cannot arise from physical
interactions of the body. Of the early modern philosophers, Baruch Spinoza alone theorizes that
the physical brain and psychical conscious mind exist as one. Body-mind monism corresponds
best with empiricism, a school of thought built on the notion that
by refraining from abstracting the human consciousness into a metaphysical ideal, thus evading
the problem of interaction faced by the dualists. In this paper, I will explain Descartes’ proposal
of dualism and the interaction issue to demonstrate how Spinoza’s mind-body monism
automatically side-steps the entailing controversies of interaction responses and proceed to
demonstrate how Spinoza triumphs in this debate due to his comparative concurrence with the
empirically-supported theory of materialism.

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René Descartes proposed the substantive split between the body and mind later coined
“dualism.” Descartes defines a body as “all that is capable of being bound by some shape, of
being enclosed in a place, and of filling up a space in such a way as to exclude any other body
from it” (“Meditations on First Philosophy” 44). Yet for Descartes, human ideas and sensations
cannot be attributed to the mechanistic workings of this body, of which the sole mode is
extension. This assertion is founded in his view that the nature of the body does not comprise
“the power of self-motion” (44). Rather, the body is a passive receptor of the active mind. To
further this claim, Descartes establishes that a stream of consciousness—prior used in the first
meditation to demonstrate a thinking thing’s existence—is all that cannot be separated from
identity. “Thought exists; it alone cannot be separated from me” (44). Accordingly as long as a
thing thinks, it exists. Descartes’ argument for dualism is therefore hinged on the foundational
cogito ergo sum which states that we are first and foremost only assured the existence of our
mental state and not of our body. Fundamentally what exists is the mind, which Descartes
believes is eternal, indivisible, and distinct of the finite body. While the mind can exist
independently, as Descartes perceives through meditation, the body does not necessarily exist.
Perhaps the most influential contention with mind-body dualism is presented by Princess
Elisabeth. She desires an enumeration of the method of the interaction of two separate substances
having distinct natures, for the mode of the body is extension yet the mode of the mind is
thought—purely psychical. How could either one influence the other if one is intangible and the
other physical? Elisabeth writes, “It seems that how a thing moves depends solely on (i) how
much it is pushed, (ii) the manner in which it is pushed, or (iii) the surface-texture and shape of
the thing that pushes it” ("From Correspondence between Descartes and Princess Elisabeth” 8).
Descartes seemingly misunderstands her inquiry to be one of epistemological conceptions of

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mind and body rather than their metaphysical interaction. Later dualists Leibniz and
Malebranche contribute their own responses in the forms of pre-established harmony and
occasionalism, respectively. It is often assumed that Descartes fails to properly answer the
interaction dilemma; while Leibniz and Malebranche merit respect in their own theories (Leibniz
contending that the two do not actually interact but whose movements are synchronized by God,
Malebranche stating that God alone causes the motions of the body), they still face controversy.
Non-materialists like these dualists posit the existence of a something which cannot by definition
be empirically proven because of its lack of physical existence. Monism alone assuredly solves
both the mind-body interaction problem and coincides most fully with the contemporary
demonstrations that empirical scientific method (rather than the abstraction of a non-physical
mind) can observably explain mental states.
Spinoza’s monism contends that modes of the body are identical to modes of the mind.
This Identity Theory argues that, rather than two distinct attribute categories of modes and their
coordinating substances, there exists only one. To elaborate, “Thinking substance and extended
substance are one and the same substance, comprehended now under this attribute, now under
that. So, too, a mode of Extension and the idea of that mode are one and the same thing,
expressed in two ways” (Spinoza 166). Essentially, the single substance that exists—in Spinoza’s
view, God—contains all possible attributes. Each attribute can only be conceived through itself;
though our perception may isolate a characteristic of a thing, it cannot be said that two
conceptually distinct attributes constitute two existentially distinct entities (147). Due to the
consolidation of mind and body as identical modes of a single substance with infinitely many
attributes, Spinoza entirely avoids the interaction problem faced by the dualists. A substance
which is numerically one and the same cannot be said to interact with itself. This monism to a

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large extent coincides with materialist theories in the agreement that all phenomena within our
world are caused exclusively by physical interaction.
Materialism attempts to ground the claims made throughout the history of philosophy
positing the existence of spiritual phenomena. It confronts the escapism tactic of explaining away
the unknown and ambiguous with an ideal, be it an ideal of perfect, immutable Forms or an
infinitely powerful and benevolent deity. Rather, it asserts that all phenomena are material and as
such are explicable in terms of particles. Such a theory has received growing support in the form
of empirical research as society acknowledges the ability for matter in motion to behave in
predictable, observable patterns. Humans often attribute things they could not explain without
proper technology to the metaphysical, a tendency which has effectively indoctrinated society to
believe in a special realm which diametrically opposes our own physical one. However, as
scientific collaboration and the collection of buildable knowledge has increased, such
phenomenon—such as weather, death, and consciousness—previously explained by referencing
infinite beings and spirit have been studied in terms of matter. To apply materialism to the mind-
body question, consciousness is dualistically attributed to the human’s unique spiritual mind
bequeathed to us by a loving, anthropomorphic God to model His image. This explanation of an
epiphenomenon receives support because we perceive both internal and external happenings that
are perceived as separate. However, consciousness has been studied as a product of physical
reactions which occur in the brain and has been proven experimentally to be affected by
alterations of the body—a feat which contradicts dualist accounts.
Contemporary psychology provides experimental evidence that perception is a product of
neurons firing and releasing chemical signals to other neurons, all of which are composed of
fundamentally similar particles of matter (which according to Einstein’s special relativity is an

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interchangeable state of energy. Monism looks better by the second). Demonstrating the
physicality of the generally conceived metaphysical phenomenon of consciousness, a study
performed at George Washington University manipulated an individual’s consciousness by
applying electrical impulses to the brain (Aldorf). The individual lost and regained consciousness
in accordance with the electrical signaling. Yet Descartes, Leibniz, and Malebranche would have
us believe that consciousness is not a product of the bodily functions but of something entirely
independent and accordingly unaffected. This is but one demonstration; an experiment at
Vanderbilt University attempted to discern whether consciousness is caused by the activation of
neurons within a certain section of the brain or by the simultaneous connection between multiple
active regions. By recruiting participants to engage in fMRI scanning, researchers found that
conscious awareness of a phenomenon—a disk flashing on a computer monitor—increased the
connectivity and total metabolic activity within the brain (Moran). Furthermore, psychology
teaches that the processes of our mind—such as decision-making, sensing, and memory
storage—can be attributed to sections within the brain as exemplified when loss of a physical
piece deprives an individual of that localized mental ability. These studies demonstrate how
mental states such as conscious awareness are merely the result of bodily functions.
Materialism garners more support as technology advances, but is Spinoza a materialist?
The short answer is no, but in comparison to Descartes, Leibniz, and Malebranche his theoretical
consolidation of mind and body coordinate most faithfully with this contemporary thought.
Spinoza does argue that the mind is simply the brain undergoing physical reactions; however, he
does not support the materialist notion that the physical is more fundamental than the psychical.
His proposition that every corporeal thing carries a coordinating idea such that the two are
inextricably bound and equally ontologically ubiquitous founds his theory that all things have

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psychical minds (Spinoza 169). Spinoza favors this panpsychism and thus attributes minds even
to inanimate entities, contrary to the materialist notion that thought arises from a unique,
distinctive series of physical occurrences. Yet Spinoza should still be respected for pioneering
the divergence from the anthropocentric notion that humans have an inimitable, spiritual “mind”
elevating our kind above purely mechanistic beasts. His mind-body monism unifies what we
perceive subjectively to be opposites in a manner reminiscent of Parmenides, but it does not
conclude that entities are fundamentally physical as they comprise equal psychical components.
Some may find materialism edifying; others may dislike its refrain from postulating when
physical mechanisms are unobservable. My argument in support of Spinoza’s mind-body theory
rather than modern dualist theory depends upon the validity of materialist philosophy.
Accordingly, we confront qualia—the properties of sensory experience. The problem posed by
qualia lies with the assertion that all mental states are physical. But through conscious experience
we seemingly gain sensory knowledge inaccessible through knowledge of its physical causes.
For example, knowing the biochemical mechanisms of an individual’s perception of the color red
without actually knowing what it is like to perceive red. The latter seems inexplicable, for it
seems that there are mental states which the materialist cannot produce with explanation of
physical mechanisms. David Lewis suggests that this experience acquisition does not grant the
individual new, physically-inexplicable knowledge but rather a purely physical ability to
perceive red (Tye). Though the individual may understand the physical mechanisms of the
perception of red, certain physical mechanisms in the form of an ability of that mental state are
absent prior to the experience. We can use this Ability Hypothesis to validate materialism, and
with the acceptance that Spinoza’s theory corresponds best with this philosophy we conclude
that he comes closest to the truth of the nature of the human mind and body, numerically one.

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Works Cited
Aldorf, Justine. "Researchers May Have Discovered The Consciousness On/Off Switch."
IFLScience. N.p., 03 July 2014. Web. 01 Apr. 2015.
Descartes, René. "Meditations on First Philosophy." Modern Philosophy: An Anthology of
Primary Sources. Ed. Roger Ariew and Eric Watkins. 2nd ed. Indianapolis: Hackett Pub.,
1998. 35-68. Print.
Descartes, René and Elisabeth of Bohemia. "From Correspondence between Descartes and
Princess Elisabeth." Trans. Jonathan Bennett. Early Modern Texts. July 5, 2013. Web.
October 2009. <http://www.earlymoderntexts.com>. Rpt. in 17th and 18th Century
Philosophy, PHI 220. Ed. Andrew Roche. 2015: 8-12. Print.
Moran, Melanie. "Network Theory Sheds New Light on Origins of Consciousness." Vanderbilt
Research. National Institutes of Health, 9 Mar. 2015. Web. 01 Apr. 2015.
Spinoza, Baruch. "The Ethics." Modern Philosophy: An Anthology of Primary Sources. Ed.
Roger Ariew and Eric Watkins. 2nd ed. Indianapolis: Hackett Pub., 1998. 144-170. Print.
Tye, Michael. "Qualia." Stanford Encyclopedia of Philosophy. Stanford University, 20 Aug.
1997. Web. 01 Apr. 2015.
 Why empiricism is best
o Only thing we can know (Hume)