[4.9.1] St Thomas Aquinas on Substance and Change

St Thomas Aquinas (1225 – 1274 AD) in his works On Being and Essence and The Principles of Nature writes about substance as a primary metaphysical category.

  • His model is an evolved version of Aristotelian hylomorphism (see [1.3.5], and for humans [1.3.7]), where substances are enduring primary existents composed of prime matter and substantial form.
  • The soul is the form of the living human body.
  • Incidental (or accidental) changes modify the substance’s incidental forms (or properties) like quality, quantity, place, while substantial change modifies its existence.

The following OntoUML diagram presents Aquinas’s model of substance and change:

Aquinas on substance and change
ClassDescriptionRelations
SubstanceAccording to Aquinas substances are what are primarily said to exist.
“[…] enduring things like men and trees and horses and the like have also come into being and are destined some day to cease to be. Such things are called substances.
contains PrimeMatter
PrimeMatter“The subject of a surface or incidental change is a substance [its incidental form]. The subject of a substantial change cannot be a substance; if it were, the result would be a modification of that substance, that is, an incidental change. But we are trying to understand how a substance itself comes into being as the result of a change. There must be a matter or subject but it cannot be matter in the sense of a substance. In order to signal this, we can call the matter prime matter, first matter. But it is important to recognize that this prime matter is not a substance, and does not exist apart from any particular substance. It is always the matter of some substance that exists.”
SubstantialForm“The form in a substantial change must be that which makes the substance to be what it is. Call it substantial form.”characterizes Substance; inherits from Form
IncidentalFormIncidental form (or accidental form) can be: “like size or location or temperature” characterizes Substance; inherits from Form
FormThe “elements of the change get the names that stick from another example, whittling wood. The term for wood in Greek is hyle and the term for shape, the external contours of a thing, is morphe. In English, form, a synonym of shape, is used to express the characteristic that the subject acquires as the result of the change, e.g. musical.”
LivingHumanBodyA living human bodysubkind of Substance
Soul“When the discussion moves on from what may be said of all physical objects as such to an inquiry into living physical things, the analyses build upon those already completed. Thus, “soul” will be defined as the form of living [human] bodies. […]
Thomas merely concludes from this fact that the soul is a ‘particular thing’ and thus a subsistent after the death of the body. He argues that what belongs to the notion of ‘this particular thing’ is only that it be a subsistent, and not that it be a substance complete in a nature. A subsistent is something with an operation of its own, existing either on its own or in another as an integral part, but not in the way either accidental or material forms exist in another. Existing on its own is not distinctive of substances alone. A chair is a particular thing, and thus a subsistent. But on Aquinas’ account it is not a substance; it is rather an accidental unity of other subsistents which may or may not be substances. A hand has an operation distinctive of it as an integral part of a living body, an operation different from the operation of the stomach; it is a particular thing and also a subsistent. (Summa Theologiae Ia.75.2 ad1; also Quaestiones Disputate de Anima 2.) And yet being an integral and functional part of a substance, it does not have the complete nature of a substance.”
inherits from SubstantialForm; characterizes LivingHumanBody
ChangeChange is can be a change of one substance into another substance, or a modification of an already existing substance.
“Aristotle had to begin with a particular example of change, one so obvious that we would not be distracted by any difficulties in accepting it as such. ‘A man becomes musical.’ Someone acquires a skill he did not previously have. Thomas pores over the analysis Aristotle provides of this instance of change and its product.
The change may be expressed in three ways:
[1] A man becomes musical.
[2] What is not-musical becomes musical.
[3] A not-musical man becomes musical.
These are three different expressions of the same change and they all exhibit the form A becomes B. But change can also be expressed as From A, B comes to be. Could 1, 2 and 3 be restated in that second form? To say ‘From the not-musical the musical comes to be’ and ‘From a not-musical man the musical comes to be’ seem acceptable alternatives, but ‘From a man musical comes to be’ would give us pause. Why? Unlike ‘A becomes B’ the form ‘From A, B comes to be’ suggests that in order for B to emerge, A must cease to be. This grounds the distinction between the grammatical subject of the sentence expressing a change and the subject of the change. The definition of the subject of the change is ‘that to which the change is attributed and which survives the change.’ The grammatical subjects of 2 and 3 do not express the subject of the change. Only in 1 is the grammatical subject expressive of the subject of the change.
This makes clear that the different expressions of the change involve two things other than the subject of the change, namely, the characteristics of the subject before (not-musical) and after (musical) the change. These elements of the change get the names that stick from another example, whittling wood. The term for wood in Greek is hyle and the term for shape, the external contours of a thing, is morphe. In English, form, a synonym of shape, is used to express the characteristic that the subject acquires as the result of the change, e.g. musical. The characterization of the subject prior to the change as not having the form is called privation. Using this language as canonical, Aristotle speaks of the subject of the change as its hyle or matter, the character it gains as its morphe or form, and its prior lack of the form as its privation. Any change will involve these three elements: matter, form and privation. The product of a change involves two things: matter and form.”
IncidentalChange“The analysis of change and the product of change begins with surface [incidental] changes [or accidental changes]. Some enduring thing changes place or quality or quantity. […]
As the analysis of incidental change makes clear, the substance previously existed without the form it acquires in the change and it could lose it and still be itself.”
inherits from Change; changes IncidentalForm
SubstantialChange“In a substantial change, the substance itself simply comes to be, or ceases to be.” inherits from Change; changes existence of SubstantialForm

Sources

  • All citations from: McInerny, Ralph and John O’Callaghan, “Saint Thomas Aquinas”The Stanford Encyclopedia of Philosophy (Summer 2018 Edition), Edward N. Zalta (ed.)
  • Kerr, Gaven : “Aquinas: Metaphysics”, Internet Encyclopedia of Philosophy
  • The Cambridge Companion to Aquinas, CAMBRIDGE UNIVERSITY PRESS, Edited by  Norman Kretzmann and Eleonore Stump, 2010

First published: 10/09/2020

[4.8] Robert Grosseteste on Exemplarism and Truth

Robert Grosseteste (1168–1253 AD) in his treatise On Truth elaborates on the concept of exemplarism and truth, and states that:

  • Platonic forms, as eternal models or examples, exist in God’s mind.
  • Things (and not just propositions) have truth-value.
  • The Aristotelian conception of truth as conformity/adequation of the speech to the things is modified by Grosseteste, by considering the speech to be that of God, the eternal Word. In this sense, each thing can have two truth-values: (1) “the eternal reason of a thing specifies the very kind of thing that thing is” – which is always true, and (2) if the thing fulfills its ethernal function – which can be true or false.
  • In this way, we can epeak or more truths, but at the end “for Grosseteste any use of the term ‘truth’ involves in some way a reference to the supreme truth, God.”

The following OntoUML diagram presents Robert Grosseteste’s model of truth:

Robert Grosseteste on exemplarism and truth
ClassDescriptionRelations
God’s(Mind)“Grosseteste’s exemplarism […] is in part an adaptation of Plato’s theory of Ideas to a Christian framework. Like other medieval thinkers, Grosseteste takes the existence of an eternal, self-subsistent realm of Platonic Ideas to be inconsistent with the dependence of all things on God. Nevertheless, following Augustine and Seneca, he does not reject the Platonic ideas outright. Rather, he treats them as eternal models (exempla) or, as he also calls them, reasons (rationes) of things in God’s mind.creates Thing
EternalWord“Grosseteste claims that the eternal Word is itself its very own conformity to itself and thus may be identified with truth.exclusive part of God’s(Mind); describes EternalModel
EternalModel“Grosseteste’s exemplarism […] is in part an adaptation of Plato’s theory of Ideas to a Christian framework. Like other medieval thinkers, Grosseteste takes the existence of an eternal, self-subsistent realm of Platonic Ideas to be inconsistent with the dependence of all things on God. Nevertheless, following Augustine and Seneca, he does not reject the Platonic ideas outright. Rather, he treats them as eternal models (exempla) or, as he also calls them, reasons (rationes) of things in God’s mind. Like the Platonic ideas, these reasons function as paradigms or models created things can accord with or fall short of. God looks to these reasons of things in creation, somewhat as a craftsman looks to the idea in his mind of what he is to make.
Given that God is absolutely simple, the reasons of things in God’s mind must in the final analysis be identified with God. Thus Grosseteste moves between speaking of the reasons in God’s mind as exemplars or models and speaking of God himself as such.”
exclusive part of God’s(Mind); model for Thing
Truthtruth (veritas) is a conformity between things and the eternal Word. […]
As for created things, their truth is their conformity to their eternal model or reason in the eternal Word.[…]
the truth of propositions—a subclass of things—is their conformity to their eternal model or reason in the eternal Word. “
Each Thing (and Proposition) can have one or, two truths:
● (1) “On the one hand, the eternal reason of a thing specifies the very kind of thing that thing is, and simply in virtue of existing as an item of a determinate kind a thing will necessarily conform to its exemplar in this respect and be true. Thus all human beings and all propositions are true, in this sense, in that they are the kinds of things they are, this being specified by their exemplar. A human being is a composite of body and soul, and a proposition is ‘the statement of one thing about another or one thing from another’ […]
● (2) “On the other hand, the eternal reason specifies the second perfection a thing ought to have but may nonetheless lack. In this sense a human being will be a false human being if, for example, she is vicious, falling short of the perfection of virtue specified in the eternal reason of a human being. Likewise, a proposition will be a false proposition if it fails to perform the function of a proposition, this being to state things as they in fact are in the world. Thus, the ordinary notion of propositional truth, described by Aristotle as ‘to so be in the thing signified as speech says,’ is a matter of a proposition’s conformity, in respect of second being, to its eternal reason, and this is for it to perform the function perfective of propositions, namely, to be in conformity to the states of affairs it asserts.”
mediates between EternalWorld and Thing
ConformityConformity or adequationcharacterizes Truth
ThingThing
PropositionProposition is a sentence with tuth-value.subkind of Thing

Sources

  • All citations from: Lewis, Neil, “Robert Grosseteste”The Stanford Encyclopedia of Philosophy (Summer 2019 Edition), Edward N. Zalta (ed.)

First published: 03/09/2020