Though born nearly a century apart in markedly different geographic and socio-cultural contexts, Denis Diderot and Baruch Spinoza followed surprisingly similar trajectories throughout their lives. The upbringing and early education of each of these intellectuals revolved around organized religion. Diderot attended a Jesuit college, graduating with special recognitions, and even pursued an ecclesiastical career for some time before stopping short of being fully ordained, going on to abandon the church altogether later in his life.1 Spinoza was similarly a star pupil in his Jewish community’s Talmud Torah school and was likely being groomed to become a rabbi before cutting his studies short, later being forced out of the community all together after being issued a writ of herem for his heretical ideas.2 Each of these thinkers would go on to abandon the organized religions in which they grew up to pursue more satisfactory answers to some of life’s greatest questions when they deemed their respective churches’ explanations insufficient. These pursuits would attract much animosity towards each of them in their own times as they audaciously disrupted the norms, forcing them each to hold back publishing some of their greatest works, which wouldn’t surface until after their deaths. The aims of these men as they contemplated a universe free of the dogmatic views forced on them from an early age would lead them each to converge upon an important question as they sought to justify their experience of nature: How is it that we perceive the world and ourselves? This question would lead Spinoza and Diderot to form vastly different conceptions of metaphysics and human nature, though, hidden within each of them can be found some interesting similarities.
Spinoza describes everything in the universe as an expression of an attribute of God, not separate from God in any way, but rather an actualization of part of his nature. In this way, all of the physical universe is an expression of God’s infinite attribute of extension, while all modes of thought are expressions of God’s infinite intellect, his attribute of thought. Importantly, though, Spinoza views these different expressions as identical since “a mode of extension and the idea of that mode are one and the same thing, but expressed in two ways.”3 Thus, an object and the idea of that object are the same thing conveyed in different forms. Following from this, the mind, as a mode of thought, is just a part of the infinite intellect of God, and as such, it is an idea which must correspond and be identical to a particular mode of extension. This mode of extension, Spinoza believes, must be the body because “we have ideas of the affections of the body” and nothing else.4 We feel the sensations of our body, what it is affected by and what occurs within it, thus our mind must be the part of God’s intellect that stores information about our body, and since we do not have knowledge of any sensations from within any other object, the body alone must be the mode of extension which our mind corresponds to, and therefore must also exist. With this in mind, the mind and the body must be one and the same thing, a piece of the infinite substance of God expressed as a mode of thought and a mode of extension respectively, a configuration which allows the mind to have knowledge of all the sensations that affect the body, and thus perceive the physical world from the body’s point of view.
Diderot takes a bit of a different approach as, though he similarly believed that the universe consisted of a single substance, he held that substance to be matter rather than God. In Diderot’s view, the entire world consists of nothing but contiguous molecules of matter. Diderot’s concept of sensibilité, would allow him to justify an explanation for sensation that avoided relying on anything immaterial. Sensibilité, for Diderot, is an indivisible property universal to all matter, one that allows any piece of matter to potentially possess consciousness and sensation. This sort of latent sensation can be activated in any molecule if it is assimilated into a living organism as “one living, sensitive molecule can melt into another one,” these molecules then become continuous, and their property of sensibilité allows sensitivity to exist “throughout the whole mass.”5 As such, all the molecules in an organism can be thought of as a bundle of imperceptibly fine continuous fibers that forms a network of sensitive threads throughout the body. A bundle of aimless sensation, however, is not enough to make a man, so additionally, to have a concept of self, Diderot believed an organism must also have memory, for, otherwise, “its life would be only an interrupted series of sensations without anything to bind them together.”6 If someone was only aware of their sensations in the moment that they sensed them and couldn’t remember what came before, their existence would be nothing but an unbounded string of sensations. As such, Diderot believed that this bundle of sensitive threads had to converge at some center that could “receive all kinds of sensations” from these threads, “register them,” and “remember them.”7 This center can essentially be thought of as Diderot’s concept of the mind as it perceives all the signals registered by every part of the body, however, unlike a typical view of the mind, this center is wholly material, a hallmark of Diderot’s philosophy made possible by his concept of sensibilité. Thus, the center of the bundle of continuous sensitive fibers that constitutes an organism is able to perceive all the sensations that occur within the body or which are the result of external impressions since all sensations are transmitted to it through the threads of the body which converge at its point.
These two views of metaphysics and human nature, on the surface, appear to radically differ, but there are key aspects of each theory that reveal interesting similarities. For one, as Diderot and Spinoza each affirm the existence of a single substance, they also each consequently conclude that the mind and body are one in the same. Spinoza views them as simply different expressions of the same thing while Diderot believes the mind is a natural consequence of the material configuration of the human body. Each of these views asserts that sensation and physicality are contained within the same thing. The key difference between them is that Spinoza believes this thing to be both a material body and a mode of thought at the same time, while Diderot commits to the thing being wholly material, albeit with the property of sensibilité. This property does add an interesting connection between the two perspectives though. Spinoza views everything in the universe as a part of God able to be expressed through an attribute of thought or extension (or infinitely many other attributes). If this conception of things is extended to the molecular level, every molecule can be thought of as a particular mode of extension that must also have a corresponding mode of thought identical to it. This mode of thought must contain everything that the molecule is affected by, how it senses and interacts with everything in the world around it, in order for God to have a complete idea of the state and identity of the molecule at any given point. Thus, when molecules converge into an organism, God’s idea of that organism can be thought of as a conglomeration of all the ideas of the individual molecules fused into a continuous mass, a singular whole rather than a combination of contiguous molecules. As such, the ideas of the individual molecules would converge into a single idea to encompass God’s conception of the body. This idea would be the mind. In this way, Spinoza’s metaphysics can be thought of as somewhat adjacent to Diderot’s concept of sensibilité. Since Spinoza’s view requires every piece of the material world to have a corresponding mode of thought within the infinite intellect of God and for each of these modes of thought to be one and the same with its mode of extension, it results in every piece of the material world to necessarily contain an awareness of itself, a sort of consciousness or sensitivity as the mind does with respect to the body.
Though this may be a radical oversimplified view of Spinoza’s conception of the universe, some correspondence between the theories of these two men seems reasonable to assume given their similar assertion that the universe consists of a single substance. Anyone who starts with this premise will logically come to some similar conclusions regarding the nature of reality as they must figure out a way to justify the existence of life and perception while limiting themselves to a single material to work with. Thus, as Spinoza and Diderot attempted to separate themselves from the explanations given to them by organized religion and form their own conceptions of the universe, they similarly chose to reject substance dualism, resulting in markedly different views and metaphysics and human nature that nevertheless each have a kind of sensitive disposition at their cores.
Endnotes:
1 Charles T. Wolfe and J.B. Shank, “Denis Diderot,” in Stanford Encyclopedia of Philosophy (Spring 2021 Edition), ed. Edward N. Zalta, Metaphysics Research Lab, Stanford University, June 19, 2019, https://plato.stanford.edu/entries/diderot/.
2 Steven Nadler, “Baruch Spinoza,” in Stanford Encyclopedia of Philosophy (Summer 2020 Edition), ed. Edward N. Zalta, Metaphysics Research Lab, Stanford University, April 16. 2020, https://plato.stanford.edu/entries/spinoza/.
3 Baruch Spinoza, Ethics (1677), 451.
4 Ibid, 457.
5 Denis Diderot, “D’Alembert’s Dream,” in Rameau’s Nephew and Other Works, trans. translated by Ralph H. Bowen and Jacques Barzun (Indianapolis: Hackett Publishing Co, Inc, 2001), 110.
6 Ibid, 99.
7 Ibid, 153.
Bibliography
Diderot, Denis. “D’Alembert’s Dream.” In Rameau’s Nephew and Other Works, translated by Ralph H. Bowen and Jacques Barzun, 89-175. Indianapolis: Hackett Publishing Co, Inc, 2001.
Nadler, Steven. “Baruch Spinoza.” In Stanford Encyclopedia of Philosophy (Summer 2020 Edition). Edited by Edward N. Zalta. Metaphysics Research Lab, Stanford University, April 16. 2020. https://plato.stanford.edu/entries/spinoza/.
Spinoza, Baruch. Ethics. 1677.
Wolfe, Charles T., and J.B. Shank. “Denis Diderot.” In Stanford Encyclopedia of Philosophy (Spring 2021 Edition). Edited by Edward N. Zalta. Metaphysics Research Lab, Stanford University, June 19, 2019. https://plato.stanford.edu/entries/diderot/.
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