84. The Soul's Union with the Body Without Intermediary

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Lecture Notes

Main Topics #

• The Problem of Intermediary Bodies: Whether a mediating substance is necessary between the immaterial soul and the material body
• Two Kinds of Parts: The distinction between quantitative parts (divisible, separable) and essential parts (matter and form)
• Form as Act of Matter: How substantial form is the actualization of matter’s potentiality, making intermediaries unnecessary
• Being and Unity: The correlation between a thing’s being and its unity; form gives being (esse) and thereby unity
• False Theories Refuted: Multiple erroneous positions including Platonist views, theories of intermediate subtle bodies, and celestial light as mediators

Key Arguments #

Against Intermediary Bodies #

• The Wax and Shape Analogy (from Aristotle’s De Anima): Just as wax and the shape impressed upon it require no third substance between them, the soul and body require no intermediary. The shape is the act of the wax’s potentiality to be shaped.

• Matter and Form are Not Two Actual Things: If form were a separate actual being, it would need a third thing to unite it to matter. But form is not actual in itself; it is the act of matter’s potentiality. Therefore, no intermediary can exist between them.

• The Agent as Sole Cause of Union: The only thing that unites matter and form is the agent (the efficient cause) that reduces matter’s potentiality to actuality. Nothing within the composite unites them.

• Being and Unity Inseparable: A thing’s being (esse) and its unity are correlative. Since the form is what gives being to the composite, and being and unity go together, the form itself, by being the act of matter, makes the thing one. An intermediary would contradict this unity.

• Substantial Form Perfects Immediately: Unlike accidental forms (which perfect only the whole), the substantial form (the soul) perfects both the whole and each part. This immediate perfection shows that no intermediary is needed.

Refutation of Specific Theories #

• Against Incorruptible Intermediate Bodies (Platonist position): This falsely imagines the soul-body union on the model of two actual things requiring a mediator. But the soul and body are not two actual existents.

• Against Subtle or Spiritual Intermediate Bodies: While the body may have subtle bodily principles involved in its operations (like what moderns call electrical impulses), these do not mediate the soul’s union with the body itself.

• Against Celestial Light as Intermediary: The theory that different heavens’ lights mediate the union of different souls (nutritive, sensitive, rational) to the body is purely fictitious and worthy of ridicule.

Important Definitions #

Quantitative Parts (partes quantitativae) #

Parts that are divisible by continuous quantity (dimensions), can exist independently, and are separable from one another. Example: the letters C, A, T in the word “cat,” which can be physically separated and rearranged.

Essential Parts (partes essentiales) #

Parts that are essential to what a thing is but are not independently subsistent and cannot be physically separated. Examples:

• The letters and the order of letters in the word “cat”
• The ingredients and ratio in a Manhattan cocktail (2 parts rye whiskey to 1 part sweet vermouth)
• The rubber and the spherical shape of a rubber ball

These parts correspond to matter and form respectively.

Substantial Form (forma substantialis) #

The principle that makes matter actually exist and gives it its specific nature. It is united to matter as act to potentiality, giving the composite being (esse), unity, and nature. The soul is the substantial form of a living body.

Accidental Form (forma accidentalis) #

A form that perfects something already existing in substance. Example: the arrangement or shape of a house. Accidental forms perfect only the whole, not the parts.

Act and Potentiality (actus et potentia) #

• Act (actus): actual existence or activity
• Potentiality (potentia): the capacity to be actualized
• Form is act; matter is potentiality. The form is the actualization of matter’s potential to be a certain kind of thing.

Examples & Illustrations #

The Word “Cat” #

The word consists of three letters (C, A, T) and their order. One might ask: are the letters and the order two different parts requiring a third to unite them? No. The order is not a separate thing from the letters; it is intrinsic to what makes those letters constitute the word “cat.” Similarly, the soul is intrinsic to the body, not a separate substance requiring a third to unite it.

The Manhattan Cocktail #

A Manhattan requires rye whiskey and sweet vermouth in a 2:1 ratio. If the ratio is not maintained (e.g., 1:1), it is not a proper Manhattan—it becomes too sweet. The ratio is not a third ingredient but is essential to what makes a Manhattan what it is. Analogously, the soul is not a third thing between matter and something else; it is what makes the body be a living body.

The Rubber Ball #

A rubber ball consists of rubber (matter) and spherical shape (form). One might imagine needing a third thing to unite the rubber with its shape. But no such intermediary exists in the ball itself. The agent (the person or machine that shapes the rubber) causes their union, but nothing within the ball mediates between rubber and shape. The shape is simply the act of the rubber’s potentiality to be shaped.

The Wooden Chair #

A chair’s legs and seat are quantitative parts that can be separated and reassembled through external mediators (glue, screws). But the soul and body are not like this. They are essential parts, like the rubber and shape of a ball.

Plato’s Sailor Analogy (Rejected) #

Plato conceived of the soul as a sailor in a boat or a man in a car—a separate substance merely inhabiting and moving the body. This view requires intermediaries for motion across distance. But Thomas rejects this: the soul is the substantial form of the body, not merely its mover.

Notable Quotes #

“The unity of a thing composed from matter and form is through the form itself, which, by itself, is united to the matter as its act. Nor is there anything uniting it, except the agent, right, that makes the matter to be an act.” — Thomas Aquinas

“A thing is said to be one in the same way that it is said to be a being.” — Principle cited by Thomas from Aristotle

“The figure is united to the wax with no body in between; therefore also the soul to the body.” — Aristotle, cited by Thomas from De Anima II

“This is fictitious and worthy of laughter.” — Thomas’s assessment (via Berquist) of the theory that celestial lights mediate different souls’ union to the body

Questions Addressed #

Q: If the soul is immaterial and the body is material, how can they unite without an intermediary substance? #

A: The soul is not a separate actual substance. As the substantial form of the body, the soul is the actualization of the body’s potentiality to be alive. Form and matter are not two separate actual things requiring external connection; rather, form is the act that makes matter actually be. No intermediary is needed because one of the “parts” (the form) just is the actualization of the other (matter’s potentiality).

Q: Doesn’t the body need a subtle or spiritual intermediary (like light or spirit) to bridge the gap between gross matter and the immaterial soul? #

A: While subtle bodily principles may be involved in the body’s operations (serving as the first instrument of the soul’s motion), they do not mediate the soul’s union with the body itself. The soul is united to the body as form to matter, immediately and without intermediary. The theories positing such intermediaries falsely imagine the soul-body union on the model of two actual things requiring a third.

Q: What distinguishes the union of soul and body from the union of two parts of a chair? #

A: A chair’s parts are quantitative parts—independently subsistent wholes that can be separated and reassembled. They are two actual things requiring a third (glue, screws) to hold them together. The soul and body are essential parts (matter and form), not quantitative parts. Form is the act of matter’s potentiality; they are united immediately as potentiality to its actualization. No third thing can mediate between them.

Q: If the agent causes the union of form and matter, doesn’t the agent act as an intermediary? #

A: No. The agent causes the union by actualizing matter’s potentiality through the form. The agent is external and efficient; it is not an intermediary within the composite itself. Once the form is present, matter and form are immediately united as act to potentiality.