Spinoza’s Criticism of Descartes’ Substance Dualism

Substance dualism is often called ‘Cartesian dualism” ?and is the assumption that mind and body are really distinct substances. Rene Descartes (1596 – 1650) was the first early modern philosopher to hold that a thinking-thing is entirely different form an extended thing and mind can exist without the body. Cartesian dualism, which started the famous mind-body problem of causal interaction, has been criticised by many, one of whom was a primary adherent, Baruch Spinoza (632-1677). This essay aims to explain and assess Spinoza’s criticism of Descartes substance dualism and see what Spinoza offers instead.

I will begin by summarizing the views of Descartes on substance and distinctiveness of mind and body and how they interact. Then I will discuss Spinoza’s objections to Descartes views in general but give more details about the ones I believe are more important. I will finish by concluding what Spinoza actually wants out of it and what he really achieves. Descartes substance dualism Rene Descartes, credited with being the “Father of Modern Philosophy”, was a substance dualist and committed to the mechanistic conception of physical world.

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Descartes believed in existence of material things and was, like most of his contemporaries, a mechanist about the properties of matter (Intro, Meditations. P. X. ). He also believed, except human beings and where minds are not interfering, the behaviour of all other things which work according to theirs laws, can be explained mechanistically. He rejected the then dominant view of Scholastic Aristotelians of many types of things, each composed of matter plus a particular form in a way that the Form or Soul affects the matter or gives life to bodies.

For Descartes “a substance is a thing which other things, such as properties or qualities or states, inhere but it does not inhere in or depend on anything else. (Principles. 51)Descartes believed that there existed two kinds of distinct substances; minds with the attribute of thinking, and bodies with the attribute of being spatially extended. And he thought there are lots of minds and lots of bodies. (Principles 52) Meanwhile, Descartes says that “minds and bodies are created by God and depend for their existence on him but nothing else. So we can conclude that in his view there exist uncreated substance, God, and two created substances, mind and body. Which are essentially distinct and can be perceived apart from one another? Yet they are still closely conjoined. At the same time, Descartes says, these substances still operate entirely in different ways. He even believed that there can be bodies without minds, and minds can survive the destruction of their corresponding bodies.

According to Cartesian Dualism, minds that are purely spiritual and non-spatial, and bodies which are spatial, can interact causally and affect each other. Descartes argues that certain mental changes, e. g. changes in one’s thought, can cause certain changes in his/her body, and vice versa, i. e. bodily damage is associated with pain; having a bad feeling about something may stop you from doing it. So Michal Della Rocca, in his book (Spinoza-2008) concludes: Descartes believed that “the interaction between mind and body happened in the pineal gland” which is located near the centre of the brain. Stanford Encyclopaedia of Philosophy) But what seems unexplained is how this interaction happens and how two completely alien substances interact? Descartes, in my opinion didn’t seem to have a satisfying answer but using what seems to be “a logically-evasive argument” he suggested that the interaction itself is managed, given and overseen by God (TR, p. 126). In Descartes view, each substance (mind or body) has one essential attribute (thinking or being extended) that constitutes its nature and essence, and to which all its other properties are referred.

He calls the other properties or features of a substance “modes” which means many mathematically explicable shapes and sizes for bodies and many ways of thinking (judging, imagining, sensing, recalling, feeling etc. ) for minds (Principles-56). Meanwhile, the fundamental feature of a mind/soul, in Descartes view, is to think not to give life or nourish, as Scholastic Aristotelians thought. Now let’s see what objections Baruch Spinoza has to Descartes. Spinoza’s criticism of Cartesian Dualism

Spinoza, having been a rationalist character and a careful expositor of Cartesianism, defines substance, attribute and mode in ways which are very close to the ones Descartes had previously given. In Ethics, he outlines his position as follows. Unity of Substance From Spinoza’s definitions and comparing them to the ones of Descartes I explained earlier, it is clear that for both philosophers a substance is self-sufficient, an attribute constitutes the essences of a substance, and modes are dependent for their existence on other things.

However, when Descartes using his analytic mode of evaluation which utilized his concept of “clear and distinct ideas” argues that minds and bodies are distinct substances but depend for their existence on God, Spinoza objects and says “One substance can’t be produced by another substance. ” (Ethics, I, p6) Michael Della Rocca, in his book (Spinoza-2008) has a good explanation of this. So, if this principle mind and body dependence to God for their existence is taken seriously, the rational conclusion would be that they can’t be substances according to Descartes own account.

Therefore, Spinoza argues that the only substance is “God” (Ethics, II. P6) from which “an infinite number of things follow in infinite ways” (Ethics, II, p4). Meanwhile, it is also important to note that for Spinoza, unlike Descartes, who believed in just two attributes, here is “infinity of attributes” that God has them all, but just two of them (thought and extension) are known to human being. We clearly see from the above two propositions that mind and body are the essence of the same substance(God) each of which is essential to it and neither can be reduced to the other; hence, substance monism and concept dualism.

Objection to lots of Minds & Bodies Existence Descartes viewing mind and body as distinct substances with attributes of thought and extension, maintains that there are lots of minds i. e. my mind, your mind, John’s mind etc. and lots of bodies, i. e. my body, the wax, etc. And they are all substances. But this view raises the question of differentiation. While all minds and bodies have the same attributes of thought or extension and thus can’t be differentiated by their attributes, how are they going to be differentiated then?

For Descartes the only thing to differentiate them may seem to be modes of substances. In other words, he may be able to differentiate the substances by appealing to their modes which means different shapes, sizes, colours etc. for bodies and different ways of thinking like feeling, guessing, remembering etc. for minds. But such an argument wouldn’t satisfy Spinoza, who argues that substance is “prior to its modifications” (Ethics, P1).

What Spinoza means here is what we really need to consider is the essence of the substance rather than its modifications. So being round or square for the rock, and recalling a word or remembering a scene for mind, can’t differentiate them as substances, because John’s mind can exist even if he is not recalling a particular name. Objection to mind-body causal interaction We saw earlier that Descartes rules out any sort of conceptual connection between attributes (thought & extension), though he accepts that mind and body can causally interact.

Spinoza, on the other hand, not only says that nothing extended is conceptually connected to something thinking, but also rules out any causal relations between thought and extension. But why? Della Rocca says “For Spinoza causal dependence amounts to conceptual dependence and thus when he says a substance is conceptually independent of everything else, he means as well that it is causally independent” (Spinoza, II, p 43) In addition, as I mentioned before, according to Spinoza thought & extension are just two of many attributes of the same substance (God or Nature), so they are of the same origin.

Spinoza argues that the sequence of ideas that is part of our account of substance under the attribute of thought represents the parallel physical sequence. So, according to him, for any physical event, there’s a matching ‘idea’ of that event and the two sequences can be said to run parallel to each other (Ethics. II. P11) Hence, this conception of the ‘relation’ between mind and body does away with the problem of interaction, because mind and body are the same substance, and thus are not “wholly alien” in character to one another.

On the other hand, Spinoza has an objection to the materialists that when they say motion in matter can cause thought, they don’t know what they are saying or mean, that is, how could motion in fundamentally spatial body cause a fundamentally non-spatial thought? This exact objection applies to Descartes too, even though he believes in conceptual independence of mind and body and doesn’t reduce thought to matter in motion. In fact, Descartes paves the way for Spinoza’s objection by arguing that mind and body are intermingled or conjoined, and as discussed earlier; interact causally through a pineal gland.

Here; Spinoza argues that when Descartes posits out causal connection like this, he doesn’t know what he means either. In other words, though we see that the sensory states correlate with how things are in our environment and the experiences of our bodies through bodily sensations and emotions show that the connection between the mind and body is very close, one still can’t conceive how a thought could be caused by a motion or how an act be caused by thought, i. e. we wouldn’t feel pain when got injured, We would merely observe the damage.

For Spinoza, such causation is nothing more than the relation whereby one thing explains another or makes it intelligible. The advantage is that it apparently escapes the problem of causal interaction that we saw put Descartes’ philosophy in really difficult situation. Not to mention it also indicates that mind is not, as thought by Descartes, superior to body. Objection to Divisibility of Substance Divisibility of substance, as Descartes argued for, is another aspect of Cartesian Dualism that Spinoza criticises. We know that Spinoza, as Descartes did, believed in physical world.

He argued that all the many kinds of different things around us could to be explained simply as ‘modes of substance. Up to this part the both philosophers agree, but when Descartes suggests that body, being a material thing, is divisible while mind or soul that is non-spatial, is not, Spinoza gets objects. Spinoza argues, suppose that a substance can be conceived as being divisible; then either its parts will also have the nature of the substance or they won’t. If they do, then (by 8) each part will be infinite, and (by 7) will be its own cause; and (by ) each part will have to consist of a different attribute. And so many substances can be formed from one, which is absurd (by 6). Furthermore, the parts would have nothing in common with their whole (by 2), and the whole (by D4 and 10) could exist without its parts and be conceived without them; and no-one can doubt that that is absurd. But if on the other hand the parts do not retain the nature of substance, then dividing the whole substance into equal parts would deprive it of the nature of substance, meaning that it would cease to exist; and (by 7) that is absurd.

So he says, although things with the attribute of extension, appear to be divisible, such as wood, they are not divisible as a substance itself, because bodies or matter, being extended is not a substance but a modification of the only substance, namely God or Nature. Conclusion The mind-body problem, originated with Descartes substance dualism in 17th century, still seems far from being solved and the question of how a mind affects a body and vice verso still hasn’t been given, in my opinion, a satisfying answer.

But it seems to me that Spinoza’s conception of the relation between mind and body are less problematic than that of Descartes. Arguing that there is only one substance (God) and thought and extension are simply God’s attributes, Spinoza apparently overcomes the problem of interaction. In other words, no longer are mind and body incompatible; no longer are they “alien” to one another, they are one and don’t require a physical organ to delineate their interaction. The main consequence of Spinoza’s characterization here is that it escapes the problem of interaction that plagues Descartes’ philosophy. ………


Descartes, “Meditations on the First Philosophy,” Translated by Michael Moriarty. Oxford University Press, 2008. Spinoza, “The Ethics,” in the Rationalists. Anchor Books, 1960. Michael Della Rocca. Spinoza” Routledge, Taylor & Francis Group 2008 Cottingham, John. “The Rationalists. ” Oxford University Press, 1988 (Stanford Encyclopaedia of Philosophy)

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