Aquinas and Plato on the Soul, Body, and Human Nature
This paper examines Thomas Aquinas's account of the soul's relationship to the human body and divine nature, as developed in the Summa Theologica, and compares it with Plato's theory of Forms and pre-existing concepts as presented in the Phaedo. Aquinas argues that the soul, while a complete species in itself, functions as the natural form of the body and is fundamentally distinct from the Divine Nature. Plato contends that goodness and being are intimately connected and that human knowledge of perfect concepts — such as equality — implies the soul's pre-existence. The paper explores where these two thinkers converge and diverge on questions of substance, knowledge, and the soul's origin.
- The Soul and the Human Species in Aquinas: Aquinas on soul, body, form, and species
- The Soul's Distinction from Divine Nature: Human soul contrasted with Divine Nature
- The Soul's Origin and Its Union with the Body: Soul's creation and its role ruling the body
- Plato's Theory of Forms and Pre-Existing Knowledge: Plato on Forms, equality, and pre-existing concepts
- Arguments Against Plato and Points of Convergence: Objections to Plato and agreement with Aquinas
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What makes this paper effective
- It systematically unpacks Aquinas's two senses of the claim "the soul is man" before broadening to questions of divine substance and the soul's origin, giving the argument clear internal logic.
- It identifies a genuine point of convergence between Aquinas and Plato — both posit a concept of perfection pre-existing in man — while honestly noting where they diverge on being and goodness.
- Primary sources (Summa Theologica, the Phaedo, and De Anima) are cited directly, grounding the philosophical claims in authoritative texts.
Key academic technique demonstrated
The paper uses comparative philosophical analysis: it first establishes one thinker's position in detail (Aquinas on the soul's nature, substance, and origin), then introduces a second thinker (Plato) whose framework overlaps on some points but diverges on others. Counterarguments raised against Plato are then used to circle back and reinforce Aquinas's position, demonstrating dialectical reasoning.
Structure breakdown
The paper opens with Aquinas's two interpretations of "the soul is man," moves to the soul's distinction from Divine Nature (with a historical survey of errors), addresses the soul's origin and union with the body, then shifts to Plato's theory of Forms and the problem of pre-existing concepts, and closes by presenting objections to Plato that inadvertently support Aquinas's view.
The Soul and the Human Species in Aquinas
Thomas Aquinas explains his statement, "the soul is man," in two senses. In the first sense, a man is composed not just of the body but also of the soul. Some suggest that "form alone belongs to the species, while matter is part of the individual, and not the species." Aquinas denies this. He maintains that the nature of a particular species is what its definition signifies, and that natural things are defined according to both their form and matter. Matter, according to him, is part of a particular species and is shared by all others under that same species: a particular man is composed of a soul, flesh, and bones, just as other men or individuals in common are. What belongs to the substance of a particular man also belongs to the substance of other individuals belonging to the same given species (Aquinas 1947).
The second sense in which the statement can be understood concerns the sensitive operations of the soul. If the operations of the sensitive soul of a given man were proper to it alone — as all such operations are attributable to man — then whatever performs those operations proper to that soul is that thing. In other words, if what the sensitive soul does is proper to it, apart from the body, because all such actions that man performs are performed by the soul only, then that which performs acts proper only to a man is a man, and not a tree or a stone.
However, the capacity to sense is an operation not only of the soul but also of the body. Sensation, Aquinas says, is an operation performed by man, but is not proper to him alone. Animals and plants can sense as well.
Aquinas further clarifies the distinction between the "inward" man and the "outward" man. In man there is an intellectual part, which is in accordance with truth; this he refers to as the "inward" man. The sensitive part of man he calls the "outward" man — the man that those whose observations of life do not exceed the physical senses take to be the whole of man.
He also refers to the hypostasis of the soul and body in the human species. This hypostasis does not refer to every particular substance, such as a hand or a foot, but to that which possesses the complete nature of its species.
Bibliography
Aquinas, Thomas. Summa Theologica. Translated by the Fathers of the English Dominican Province. Benzinger Brothers edition, 1947. http://www.cccel.org/a/aquinas/summa.home.html
Aristotle. De Anima (Books II and III). Translated by D. W. Hamlyn. Paperback. Clarendon Press reprint, 1993.
Plato. Phaedo (360 BC). Translated by Benjamin Jowett. http://www.constitution.org/pla/phaedo.htm
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