70. Reason, the Brain, and the Immateriality of the Soul

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Lecture Notes

Main Topics #

Continuous and Non-Continuous Knowledge #

• The central paradox: A continuous thing (like a square or geometric figure) is known by reason perfectly in the form of a definition—yet the definition itself is not continuous
• A definition like “equilateral and right-angled quadrilateral” has genus and differences that do not meet at a common boundary
• This contrasts with the thing known, which is continuous

The Principle of Reception #

• Core principle: “Whatever is received is received in the receiver according to the condition of the receiver”
• The way knowledge is received depends on the nature of the knower, not the nature of the thing known
• Example: A teacher lectures to 30 students who hear the same content, yet each receives it differently according to their own condition (imagination, intelligence, etc.)

Implications for the Soul’s Immateriality #

• If reason receives a continuous thing in a non-continuous way, reason itself cannot be continuous
• If a body is continuous and reason is non-continuous, then reason is not a body
• Therefore, the soul has an operation (understanding the universal) that is not in the body
• Since being precedes doing, if the soul does something not in the body, its existence is not entirely immersed in the body

Key Arguments #

Against the Brain Being the Organ of Thought #

The Flawed Inference:

• Common argument: “If the brain is the organ of thought, then a blow to the brain interferes with thinking. A blow to the brain does interfere with thinking. Therefore, the brain is the organ of thought.”
• This commits the logical fallacy of affirming the consequent
• Form: If A, then B. B is true. Therefore, A is true. (Invalid form)

The Light Bulb Counterexample:

• If I break a light bulb in a dark room, it interferes with seeing you, but this doesn’t make the light bulb the organ of sight
• The light bulb affects the object of sight (by removing illumination of the object), not the organ of sight
• Similarly, a blow to the brain may interfere with imagination (which requires bodily images), thus indirectly affecting thinking, without making the brain the organ of thought itself

Two Ways to Interfere with a Power’s Act:

1. Interfere with the organ itself (e.g., damaging the eye damages the power of sight)
2. Interfere with the object or conditions necessary for the power’s exercise (e.g., removing the object from view, removing light)

The Logical Distinction:

• To properly conclude that the brain is the organ of thought requires a separate argument proving reason is not a body
• Once established that reason is not a body (via the continuity argument), the brain cannot be the organ of universal thought
• The brain’s role must be on the side of the object (imagination, which requires images), not the organ

The Continuity Argument for Immateriality #

Premises:

1. A continuous thing is known perfectly by reason in the form of a non-continuous definition
2. Whatever is received is received according to the condition of the receiver
3. Therefore, reason must itself be non-continuous
4. A body is continuous; reason is non-continuous
5. Therefore, reason is not a body
6. Understanding is a function of the soul, and understanding is non-bodily
7. Being precedes doing—one must exist to perform an action
8. Therefore, the soul’s existence is not entirely immersed in the body

Important Definitions #

Continuous (τὸ συνεχές) #

• That whose parts meet at a common boundary (e.g., two semicircles of a circle meeting at the diameter)
• Divisible forever (infinitely divisible)

Touching (ἁπτόμενα) #

• Things whose limits are together but not identical (e.g., two rooms sharing a wall)

Next (ἐφεξῆς) #

• Things between which there is nothing of the same kind (e.g., neighboring houses without a shared wall)

The Object of Reason #

• The what it is (τὸ τί ἐστι) of something that can be sensed or imagined
• Always universal in character
• Examples: what a triangle is, what a square is, what a man is

Examples & Illustrations #

The Light Bulb Example #

• A light bulb in a dark room is necessary for seeing, but breaking it doesn’t prove it’s the organ of sight
• Illustrates the difference between:
  • Interfering with the organ (damaging the eye)
  • Interfering with the object (removing the light source)

The Definition of Square #

• Definition: “equilateral and right-angled quadrilateral”
• The genus (quadrilateral) and differences (equilateral, right-angled) do not meet at a common boundary
• Yet this non-continuous definition perfectly expresses a continuous thing

Brain Stimulation Research #

• When scientists stimulate part of the brain and a person experiences a mental image, they may conclude “thinking happens here”
• But the person is actually imagining (in the brain), not understanding
• Images and understanding are closely tied but distinct
• Notably, brain stimulation has never produced the experience of “making a choice,” suggesting the will is immaterial

The Syllogism Example #

• Major premise: Every mother is a woman
• Minor premise: No man is a woman
• Conclusion (next thought): No man is a mother
• The thoughts are “next” to each other (not continuous), showing thoughts are not bodies

Questions Addressed #

Why does a blow to the brain interfere with thinking if the brain isn’t the organ of thought? #

• Because the brain is necessary for imagination, which provides the images reason needs to work with
• Interfering with imagination (which is bodily) can indirectly interfere with understanding
• But this shows the brain’s role is on the side of the object, not the power itself

How can reason know a continuous thing in a non-continuous way? #

• Not due to the thing known (which is continuous) but due to the condition of the knower
• Reason itself is non-continuous, so it receives continuous knowledge in a non-continuous form (as definition with distinct genus and differences)

Does this prove the soul is immaterial? #

• Yes, insofar as understanding the universal is not a continuous, bodily activity
• Since the soul is the principle of this non-bodily operation, the soul’s existence cannot be entirely immersed in the body
• Though the soul requires a body for imagination to provide material for thought while embodied

If reason isn’t in the brain, how is understanding immaterial? #

• Understanding (of universals) doesn’t take place in a body because it doesn’t involve continuity/parts
• The brain provides necessary conditions (images) but is not the seat of understanding itself
• Reason operates on images but transcends the bodily image in grasping the universal

Notable Quotes #

“Whatever is received is received in the receiver according to the condition of the receiver.”

• Central principle explaining why reason receives continuous things in non-continuous form

“It’s a defect in form in one case, and in the other case, there’s a defect in the matter. You have to avoid both of those.”

• On the two ways an argument can fail: either the logical form is invalid or the premises are false

“Just like in calculating, when you add, subtract, multiply, or divide, if you have a wrong number, then the result is not going to be good; or if you have the right number but you didn’t add correctly, either one would have a problem.”

• Analogy showing that both form and matter matter in reasoning

“You don’t understand the continuous well, you can’t understand well all the reasons we have for thinking that reason is not a body.”

• On the foundational importance of grasping continuity for natural philosophy

“If your being or existence was only in the body… then what you do would only be in the body and through the body.”

• On why the soul’s immaterial operations prove its existence transcends the body