Mind as Immaterial Substance - Lecture 2

Foundations of Substance Dualism and the Nature of Mind

• Definition of Substance Dualism: This is the philosophical view, famously associated with René Descartes, that the mind is a fundamental kind of thing just as physical matter is. It positions conscious stuff (consciousness or mentality) as an immaterial substance distinct from physical substance.

• Substance vs. Property: A substance is defined as something that does not depend for its existence on anything else (at least no other finite thing). While Descartes believed everything ultimately depends on God, he categorized the finite world into two distinct substances: the mental and the physical.

• Clarification on "Immaterial Substance": Descartes does not suggest that the mind is "immaterial goop" or like "ectoplasm" (e.g., from Ghostbusters). Describing it as "immaterial material" would be a contradiction. Instead, the mind is a substance in the sense of being a self-subsisting, non-physical entity.

• The Infinite Substance: Beyond the two finite substances (mind and body), Descartes posited the existence of an infinite substance at the root of all reality, which he called God.

Historical and Conceptual Perspectives on the Soul

• Platonic Roots: Descartes’ use of the word "soul" connects to Plato, an early substance dualist. Plato believed the soul was an immaterial substance that:

  • Dwelt in the realm of the Forms.

  • Came into being as a person and continued to exist after death.

  • Is simple, divine, immutable (unchangeable), and imperishable.

  • Is a "divine-like being" similar to the gods.

• Implications of Plato's View: This perspective allows for reincarnation (the soul entering a different body) or the soul living a separate existence after the body dies. There is a philosophical debate (supported by Kim and questioned by John Locke) regarding whether we are souls or merely have souls.

• Alternative Conceptions of the Soul: The lecture distinguishes the Cartesian/Platonic "soul" from other common usages:

  • Emotional Core: Using "soul" to describe the center of one's emotional being.

  • Aristotelian/Thomistic View: Following Aristotle and Thomas Aquinas, the soul is seen as essentially tied to the body, often related to the concept of "form" or "personal identity" rather than an independent immaterial substance.

  • Religious/Moral Context: References to "shaping," "purification," or "salvation" of the soul often refer to a different concept than the metaphysical substance dualism discussed in this context.

Cartesian Arguments from Epistemology and Doubt

• Argument 1: The Argument from Doubt (p. 36):

  • Premise 1: I am such that my existence cannot be doubted (The Cogito: "I think, therefore I am"). To doubt one is thinking, one must think, creating a logical contradiction.

  • Premise 2: My body is not such that its existence cannot be doubted. One could be dreaming, deceived by aliens, or hallucinating their physical form.

  • Premise 3: Therefore, I am not identical with my body.

  • Conclusion: The thinking thing (mind) is not identical with the physical body.

• Mathematical Doubt: Descartes notes one can even attempt to doubt that $7 + 7 = 14$, though it is difficult.

• Weakness of Argument 1: Critics argue that just because one can imagine or doubt identity does not mean two things are actually different. This is illustrated by the Mark Twain/Samuel Clemens Analogy: One might know Samuel Clemens and Mark Twain under different descriptions and doubt they are the same person, even though they are identical.

The Asymmetry of Transparency and Public Access

• Argument 2: Transparency:

  • Premise 1: The mind is transparent. Nothing can be in the mind without the subject knowing it in the moment (e.g., even a subliminal message flashing in a movie is perceived in the mind for that moment, even if forgotten later).

  • Premise 2: The body is not transparent. One can have a silent illness or internal processes occurring without any awareness.

  • Objection: Sigmund Freud’s theories of the subconscious suggest that much of the mind is hidden, challenging the idea of total transparency.

• Argument 3: Privileged Access:

  • Premise 1: Each mind has a unique subject with direct access to its contents. You know your memories and perceptions directly; others only know them indirectly by asking you.

  • Premise 2: Material bodies have no privileged knower. Knowledge of material things (like the brain) is public and intersubjective. A scientist with a scanner or a surgeon could potentially know more about your brain than you do.

  • Conclusion: Because of this asymmetry in access, minds are not identical to material bodies.

Metaphysical Arguments: Essential Nature and Conceivability

• The Concept of Essence: An essential property is a necessary property a thing cannot fail to have; it is the nature of the thing that exists across all possible worlds.

• Argument 4: The Essential Nature Argument (p. 38):

  • Premise 1: My essential nature is to be a thinking thing (a person must think to exist as a person).

  • Premise 2: My body’s essential nature is to be an extended thing in space (occupying three dimensions).

  • Premise 3: My essential nature does not include being an extended thing in space (I can conceive of being a disembodied mind).

  • Conclusion: I am not identical with my body.

• Conceivability vs. Possibility: A major objection to this is that just because something is conceivable does not mean it is logically possible. This is illustrated by Goldbach’s Conjecture: One can conceive of the conjecture (every even number > 2 is the sum of two primes) being proven true or false, but mathematically, only one of those outcomes is logically possible. If minds are actually brains, then a disembodied mind might be conceivable but logically impossible.

• Argument 5: Modal Argument (p. 39):

  • Premise 1: If anything is material, it is essentially material (e.g., an immaterial statue or immaterial water is impossible).

  • Premise 2: It is possible that I am immaterial (I can conceive of a possible world where I exist without a body).

  • Premise 3: Therefore, I am not essentially material.

  • Conclusion: I am not material.

The Necessity of Identity and the 'Time Worm' Problem

• Argument 6: Identity over Time (Reductio):

  • Symmetry Assumption: Assume I am identical with my body.

  • Fact: In the year $2001$, the specific particles making up my current body did not exist (biological particles switch out over time).

  • Contradiction: I existed in $2001$, but my body (this specific assemblage) did not. Therefore, I cannot be identical to my body.

• Response: The Time Worm/Animal Identity: Physicalists argue that a body is not just a pile of particles but a complex animal or a "time worm" that exists across a timeline (e.g., from $1980$ to $2020$) and retains identity despite changing parts.

• Argument 7: Necessity of Identity (NI):

  • The NI Principle: If $x = y$, then necessarily $x = y$. Identical things must be identical in all possible worlds (e.g., Water and $H_2O$; Cicero and Tully).

  • Application: If I were my body, I would be my body in every possible world. However, it seems possible I could have had a different body (e.g., born left-handed or with a slightly different brain). If it is possible for me to exist with a different body, then I am not identical to my current body.

Leibniz’s Mill and the Argument from Perception

• Argument 8 (p. 43):

  • Premise 1: Thoughts and consciousness exist.

  • Premise 2: Properties like thoughts must be instantiated in an object or substance.

  • Premise 3: Material beings (brains/machines) cannot be the subject of thoughts.

  • Conclusion: Thoughts must occur in immaterial mental substances.

• The Mill Illustration (p. 44): Leibniz suggests that if we enlarged a thinking machine (like a mill) and walked inside, we would only see "pieces which push against one another." Mechanical collisions, pushings, and pullings explain physical movement but do not explain or reveal perception. Perception must therefore reside in a simple, non-composite substance.

• Challenging the Premise: One can resist this by arguing that matter can think (panpsychism or non-Western views where atoms or trees have souls), but the modern Western view of matter usually denies this capacity, making Leibniz's argument difficult for materialists to answer without further explanation.