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Res extensa
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Res extensa is one of the two substances described by René Descartes in his Cartesian ontology[1] (often referred to as "radical dualism"), alongside res cogitans. Translated from Latin, "res extensa" means "extended thing" while the latter is described as "a thinking and unextended thing".[2] Descartes often translated res extensa as "corporeal substance" but it is something that only God can create.[3]
Res extensa vs. res cogitans
[edit]Res extensa and res cogitans are mutually exclusive and this makes it possible to conceptualize the complete intellectual independence from the body.[2] Res cogitans is also referred to as the soul and is related by thinkers such as Aristotle in his De Anima to the indefinite realm of potentiality.[4] On the other hand, res extensa, are entities described by the principles of logic and are considered in terms of definiteness. Due to the polarity of these two concepts, the natural science focused on res extensa.[4]
In the Cartesian view, the distinction between these two concepts is a methodological necessity driven by a distrust of the senses and the res extensa as it represents the entire material world.[5] The categorical separation of these two, however, caused a problem, which can be demonstrated in this question: How can a wish (a mental event), cause an arm movement (a physical event)?[6] Descartes has not provided any answer to this but Gottfried Leibniz proposed that it can be addressed by endowing each geometrical point in the res extensa with mind.[6] Each of these points is within res extensa but they are also dimensionless, making them unextended.[6]
In Descartes' substance–attribute–mode ontology, extension is the primary attribute of corporeal substance. He describes a piece of wax in the Second Meditation (see Wax argument). A solid piece of wax has certain sensory qualities. However, when the wax is melted, it loses every single apparent quality it had in its solid form. Still, Descartes recognizes in the melted substance the idea of wax.
See also
[edit]References
[edit]- ^ Principia Philosophiae, 2.001.
- ^ a b Bordo, Susan (2010). Feminist Interpretations of Rene Descartes. University Park, Pennsylvania: The Pennsylvania State University Press. p. 59. ISBN 978-0271018577.
- ^ Schmaltz, Tad (2008). Descartes on Causation. New York: Oxford University Press. pp. 46. ISBN 9780195327946.
- ^ a b Aerts, Diederik; Chiara, Maria Luisa Dalla; Ronde, Christian de; Krause, Décio (2018). Probing the Meaning of Quantum Mechanics: Information, Contextuality, Relationalism and EntanglementProceedings of the II International Workshop on Quantum Mechanics and Quantum Information. Physical, Philosophical and Logical Approaches. New Jersey: World Scientific Publishing. p. 134. ISBN 9789813276888.
- ^ Cavell, Richard (2003). McLuhan in Space: A Cultural Geography. Toronto: University of Toronto Press. p. 83. ISBN 0802036104.
- ^ a b c Callicott, J. Baird (2013). Thinking Like a Planet: The Land Ethic and the Earth Ethic. New York: Oxford University Press. p. 189. ISBN 9780199324897.
Res extensa
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Res extensa is a central concept in the philosophy of René Descartes, denoting the extended substance that constitutes the essence of corporeal or material reality, characterized fundamentally by spatial extension in length, breadth, and depth.[1] This term, translating from Latin as "extended thing," stands in opposition to res cogitans, or "thinking thing," which represents the non-extended, immaterial substance of the mind or soul.[2] Introduced in Descartes' Principles of Philosophy (1644), res extensa forms the basis of his substance dualism, positing two fundamentally distinct kinds of substances: one defined by thought and consciousness, the other by physical extension and divisibility.[1]
Descartes' dualism, articulated through res extensa and res cogitans, resolves the mind-body problem by asserting their real distinction, provable through clear and distinct ideas: the mind can be conceived without extension, and body without thought.[1] In res extensa, attributes such as figure, motion, position, and divisibility inhere, but qualities like color, hardness, or sound are not essential; they arise from the interaction between extended substance and the senses.[1] This framework underpins Descartes' mechanistic view of the physical universe, where all corporeal phenomena, from simple particles to complex organisms, operate according to laws of motion and extension without inherent mental properties.[3]
The concept has profound implications for metaphysics, epistemology, and the philosophy of mind, influencing debates on the interaction between mind and body—often localized by Descartes in the pineal gland[4]—despite their ontological separation.[1] Critics, including later philosophers, have challenged the causal interaction problem inherent in dualism, arguing that non-extended thought cannot efficiently cause changes in extended matter.[2] Nonetheless, res extensa remains a cornerstone of Cartesian philosophy, shaping modern discussions in neuroscience, psychology, and ontology by emphasizing the primacy of extension as the defining mark of the material world.[5]
[7][6][17]
Philosophical Origins
Descartes' Formulation
René Descartes introduced the concept of res extensa as part of his dual substance ontology in the 17th century, developing it amid his methodological skepticism to establish foundations of certain knowledge. Through his method of doubt, outlined in Meditations on First Philosophy (1641), Descartes systematically questioned sensory perceptions and external realities to arrive at indubitable truths, ultimately positing two fundamental substances: thinking (res cogitans) and extended (res extensa). This framework emerged from his quest for epistemic certainty, where doubt revealed the mind's immediate self-awareness, paving the way for clear and distinct ideas about corporeal nature.[6] In Principles of Philosophy (1644), Descartes explicitly defines res extensa as the essence of corporeal substance, consisting solely in extension in length, breadth, and depth. He argues that this extension constitutes the principal attribute of matter, without which no body can be conceived, distinguishing it from incorporeal thinking substance.[7] Extension, for Descartes, is not merely a property but the very nature of material things, infinitely divisible and filling space without voids.[6] Descartes describes res extensa as the domain of material bodies that are divisible, occupy space, and possess primary qualities such as shape, size, and local motion, all derived from extension. These qualities are objective and intelligible through reason, unlike secondary sensory qualities (e.g., color, taste) that depend on the perceiver. In Principles of Philosophy, Part II, Section 4, he emphasizes that the essence of body lies in its extended nature, allowing for configurations like figures and movements that explain physical phenomena mechanistically.[7] Bodies, as modes of res extensa, interact through contact and motion in a plenum, governed by laws of nature established by God.[6] To illustrate how extension endures amid perceptual changes, Descartes employs the wax example in the Second Meditation of Meditations on First Philosophy. He considers a fresh piece of beeswax—hard, yellow, fragrant, and malleable—perceived through senses. When heated, it loses these sensible properties, becoming soft, odorless, and liquid, yet remains the same wax. Sensory imagination fails to grasp its unity, but the mind perceives it as "something extended, flexible, and changeable," revealing extension as its invariant essence.[8] This demonstrates that true knowledge of material bodies derives from intellectual apprehension of their spatial dimensions, not fleeting sensory impressions.[6]Precursors in Ancient and Medieval Thought
In ancient Greek philosophy, the concept of extended substance found early expression in atomism, particularly through the works of Democritus (c. 460–370 BCE) and later Epicurus (341–270 BCE). Democritus posited that the physical world consists of indivisible atoms—solid, extended particles possessing shape, size, and weight—that move eternally through an infinite void, or empty space, which allows for their separation and combination to form all perceptible bodies.[9] These atoms are the true realities, while sensory qualities like color or taste are mere conventions arising from their arrangements in the void.[10] Epicurus refined this view, emphasizing that atoms are unchangeable bodies without internal void, varying indefinitely in shape and capable of motion solely through the void, which provides no resistance and enables all natural phenomena.[11] Aristotle (384–322 BCE) offered a contrasting yet influential framework in his hylomorphism, where matter (hylē) serves as the underlying substrate that supplies potentiality and extension to substantial forms, composing all natural bodies as unified compounds of matter and form. In Physics Book IV, Aristotle argues that extension (diastēma), understood as dimensional interval or magnitude, is not an independent entity or separate void but an intrinsic property of body itself, inseparable from the surfaces and limits of material things; there is no extension apart from bodies, as place is merely the innermost boundary of a containing body.[12] Similarly, in Metaphysics Book Z, matter (hylē) is described as the indeterminate potential that, when informed, yields extended substances capable of change and actuality, distinguishing physical entities from purely formal or immaterial beings.[13] Medieval scholasticism built upon Aristotelian ideas, with Thomas Aquinas (1225–1274) synthesizing them into a Christian metaphysical system that defined bodily substance as inherently extended in three dimensions, informed by accidental qualities while rooted in prime matter and substantial form. In Summa Theologica (I, q. 3, a. 1), Aquinas contrasts divine simplicity with corporeal substance, noting that bodies are composites divisible by their quantitative extension—length, breadth, and depth—which marks them as material and potent to receive forms, unlike the indivisible simplicity of spiritual substances. This view integrates Aristotle's hylomorphism by positing that extension arises from the union of matter and form, providing the spatial framework for all created physical entities.[14]Core Concepts
Definition of Extension
In René Descartes' philosophy, extension serves as the fundamental and essential attribute of res extensa, or corporeal substance, defined as the possession of three spatial dimensions: length, breadth, and depth. This extension constitutes the sole nature of material bodies, distinguishing them from non-extended substances. As Descartes articulates, "the nature of body consists not in the fact that it is a thing that is hard or heavy or coloured, or that admits of any other such property, but simply in its being an extended thing."[15] Consequently, res extensa is inherently measurable and occupies space, with its existence verifiable through clear and distinct intellectual perception rather than sensory illusion. Unlike secondary qualities such as color, taste, or hardness, which are mind-dependent and arise from the interaction between extended objects and the senses, extension remains primary and independent of perception. These secondary qualities can be altered or removed without destroying the body's essential nature; for example, a colored object retains its extension even if deprived of color through imagination or alteration.[15] Extension alone defines the substance, rendering res extensa infinitely divisible into parts, with no minimal indivisible units like atoms, as any portion of extension can be further subdivided in thought.[15] Mathematically, Descartes aligns extension with the continuous framework of Euclidean geometry, treating it as the "quantity" studied by geometers—encompassing divisibility, shape, and position in a uniform spatial medium.[15] This conceptual continuity implies an infinity of parts within any extended body, mirroring the endless divisibility of geometric lines and surfaces. For instance, the extension of a line segment lies in its measurable length, wholly independent of any superimposed color, underscoring extension's autonomy from sensory attributes. This foundational role of extension underpins the material properties of bodies, such as their shapes and sizes.Attributes and Properties
In Descartes' philosophy, the principal attribute of res extensa—extension in length, breadth, and depth—gives rise to secondary properties understood as modes that modify this extension without constituting independent attributes. These include figure (or shape), which denotes the boundaries of extended substance; quantity, encompassing magnitude or size as a measure of extension; and qualities such as motion and position, which describe changes or relations within extended space.[16] All such modes are inherently tied to and reducible to extension, ensuring that res extensa remains a unified, homogeneous substance devoid of inherent qualities like color or weight, which are merely apparent effects of configuration and motion.[16] The mechanistic worldview underpinning res extensa posits that all phenomena arise from local motion and direct contact between extended parts, governed by deterministic laws without purpose or teleology. Descartes outlined three laws of nature in this framework: the persistence of motion (or rest) unless altered by external causes; that all motion is of itself in straight lines, with specific rules for redirection in collisions; and the conservation of the total quantity of motion, whereby in collisions a body loses none of its motion if colliding with a stronger body, but transfers motion to a weaker one. This contact-based mechanics excludes action at a distance or final causes, reducing the operations of res extensa to rearrangements of its parts, as elaborated in his physics where God continually sustains these laws but imparts no ongoing teleological direction.[16] A key property of res extensa is its infinite divisibility, whereby any portion can be subdivided into smaller extended parts, each retaining the attribute of extension and thus the nature of corporeal substance. This divisibility underpins Descartes' corpuscular theory of matter, envisioning the universe as composed of indefinitely small particles (corpuscles) of varying shapes, sizes, and motions, all derived from a single extended matter without voids.[16] For instance, elasticity in bodies like springs is explained not as an intrinsic quality but as the result of tightly coiled, hook-like particles that resist deformation through their configuration and subsequent motion upon release, while fluidity in substances like water arises from smoother, more loosely arranged particles permitting easier passage and rearrangement via contact. These examples illustrate how complex properties emerge mechanistically from the modes of extension, reinforcing the reduction of all material diversity to geometric and kinematic principles.[16]Relation to Dualism
Contrast with Res Cogitans
In René Descartes' substance dualism, res cogitans—the thinking substance—constitutes an unextended, indivisible entity whose essential attribute is thought, manifesting in modes such as doubt, understanding, affirmation, denial, willing, and unwilling.[17] This stands in direct metaphysical opposition to res extensa, the extended substance, which is defined solely by its spatial dimensions of length, breadth, and depth, rendering it divisible and inherently corporeal.[7] Whereas res extensa pertains to the public, measurable realm of physical objects governed by mechanical laws of motion and quantity, res cogitans resides in the private, immaterial domain of consciousness, accessible only through introspection and characterized by qualitative ideas rather than spatial properties.[6] A central challenge in this dualism emerges from the causal interaction problem: how an unextended, non-spatial mind can affect or be affected by an extended body, such as when volition prompts physical action like raising an arm.[6] Descartes addressed this by positing that the interaction occurs principally in the pineal gland, a small, unpaired structure in the brain that he identified as the "seat of the soul," where animal spirits mediate between mental inclinations and bodily movements.[4] The following table enumerates key attributes contrasting the two substances, drawn from Descartes' formulations:| Aspect | Res Extensa (Extended Substance) | Res Cogitans (Thinking Substance) |
|---|---|---|
| Principal Attribute | Extension (spatial dimensions: length, breadth, depth) | Thought (cognition and mental acts) |
| Divisibility | Naturally divisible into parts | Utterly indivisible, without real parts |
| Essential Nature | Corporeal, public, and measurable (quantitative modes like shape, motion) | Immaterial, private, and conscious (qualitative modes like ideas, sensations) |
| Representative Examples | Quantity of matter, position in space | Doubt, understanding, will |