Unicity of substantial form
| Latin | Unicitas formae substantialis |
|---|---|
| Treatise | Summa theologiae I, question 76, articles 3–4 |
| Controlling authority | Council of Vienne; Catechism 365 |
| Doctrinal standing | The rational soul as the form of the body is defined; that there is no second substantial form in man is the characteristic Thomistic thesis |
| School | Thomism |
| Branch | Natural philosophy |
Unicity of substantial form is the Thomistic thesis that a complete substance has one substantial form only, so that in man the intellective soul is the single form by which the body is human, living, and sensing.
One form, one substantial being
Summa theologiae I, question 76, article 3, denies a second soul in man. Article 4 denies any other substantial form. A substantial form gives being simply. Accidental forms give being such. If a second substantial form were added, either it would be only accidental, or the thing would not be one substance. The intellective soul therefore gives the body its whole substantial being. Vegetative and sensitive operations are present as grades virtually contained in that one form.[1]
The 1913 Catholic Encyclopedia article on form states the general scholastic grammar of substantial form. The article on Thomism names the unity of substantial form in man as a characteristic Thomist position, attacked by Kilwardby and Oxford, and later associated with Vienne's definition against Olivi.[2][3]
Defined unity, school unicity
The Council of Vienne defined that the rational soul is of itself and essentially the form of the human body. The Catechism of the Catholic Church, 365, repeats that the soul is the form of the body. Those sentences are dogma. They close any anthropology in which the intellective soul is not the form. Thomists take them also to close a leftover form of corporeity. That further step is the school thesis called unicity.[4][5]
A Catholic must confess the defined unity. He is not required to recite the pentagon-and-triangle analogy as a creed. He may not split the man into two complete substances, or treat the corpse as still a human substance by a remaining substantial form of the body. The exact mapping of Vienne onto later technical vocabulary remains theology.
Objections from tomb and Eucharist
Opponents asked how the dead body is the same body, how Christ's body in the tomb is true, and how Eucharistic accidents remain. Aquinas's answers do not restore a second substantial form. The corpse has accidental dispositions that make it identifiable and raisable. Christ's body in the tomb remained united to the Word. Eucharistic accidents remain by divine conservation without their connatural substance, which is a different question from the number of forms in a living man.
The correctoria of the 1270s turned these objections into a pamphlet war. Unicity survived as the Dominican Thomist line. Plurality of forms remained a Franciscan and eclectic alternative. The later conciliar definition did not reprint either pamphlet. It defined the soul as form. Thomism reads that definition with unicity as its inner grammar.
Theological fruit
Unicity keeps the human person one. It keeps death a real separation, not a reshuffling of leftover forms. It keeps the resurrection a restoration of the same man, not the assembly of a committee. It keeps the Incarnation the assumption of one human nature. Those are the fruits. The thesis is their servant.
The soul is the form of the body. Unicity of form is the Thomistic thesis serving that definition. A man is not a spirit occupying an independent machine, and a corpse is not still a living substance. Between those denials the school thesis does its work.
References
- Back to citation Thomas Aquinas, Summa theologiae I, question 76 — Primary hylomorphic anthropology: the intellective soul as form of the body and the rejection of a plurality of substantial forms in man.
- Back to citation Catholic Encyclopedia (1913), Thomism — Public-domain history of Thomist principles, the correctoria after 1277, the unicity of substantial form, and the Leonine restoration.
- Back to citation Catholic Encyclopedia (1913), Form — Public-domain account of substantial and accidental form in scholastic philosophy.
- Back to citation Council of Vienne, Fidei catholicae — Conciliar definition that the rational soul is of itself and essentially the form of the human body, against any denial of that substantial unity.
- Back to citation Catechism of the Catholic Church, 355–368 — Authoritative anthropology of the human person as a unity of body and soul, the soul as form of the body, and the soul's immediate creation and immortality.