{{Short description|Philosophical concept}}
{{more citations needed|date=November 2022}}

'''Substantial form''' is a central philosophical concept in [[Aristotelianism]] and, afterwards, in [[Scholasticism]]. The ''form'' is the [[Aristotle's theory of universals|idea]], existent or embodied in a being, that completes or actualizes the potentiality latent in the matter composing the being itself. For [[Aristotle]], in fact, ''[[matter]]'' is the basis of all that exists; it comprises the ''[[Potentiality and actuality (Aristotle)|potentiality]]'' of everything, but of itself is not actually anything. A determinate thing only comes into being when the ''potentiality'' in matter is converted into ''[[Potentiality and actuality (Aristotle)|actuality]];'' this is achieved by the substantial form. It is ''substantial'' because it is the principle by which a material kind of thing is recognised as such.<ref>"Greek Philosophy" entry in [[Peripatetic school#CITEREFSeyffert1895|Seyffert 1895]], p. 482</ref>

This concept was designed by [[Aristotle]] to explain several phenomena considered perplexing in the ancient world. One was how physical things can exist as certain types of intelligible things, ''e.g.'', [[Argos (dog)|Argos]] and [[Garmr]] are both dogs despite being very different because they have the same type of substantial form: it is the substantial form that makes the physical thing [[Intelligibility (philosophy)|intelligible]] as a particular kind of thing; in other words, such is the Aristotelian solution of the [[problem of universals]]. Another one was how the activities of physical things can transcend the limitations of matter to different degrees (for Aristotle, matter was considered unable of any kind of self-organization): [[plant]]s through their vegetative substantial form transcend the capacities of inanimate matter via growth and nutritive activities; [[animal]]s through their sentient substantial form by sensation, perception and emotions; and [[human]]s by their rational substantial form, so making them "[[rational animal]]s". A third one was how one physical thing can change into another, ''e.g.'' the tiger that eats an antilope not only ends the ability of the antilope's substantial forms to continue animating its prime matter but also enables that same prime matter to become absorbed or animated by the tiger's substantial form. For Aristotle, prime matter is the ultimate principle of physicality and has the potency to being activated by substantial forms into physical entities. Without this potency of prime matter, in Aristotle's opinion, change would either be impossible or would require matter to be destroyed and created rather than altered.

Aristotle's doctrine of substantial form animating prime matter differs from [[Plato]]'s [[theory of forms]] in several ways. Unlike substantial forms, Platonic forms or ''[[idea]]s'' exist as exemplars in the invisible world and are imposed by a supreme god ([[Demiurge]] in some translations of the ''[[Timaeus (dialogue)|Timaeus]]'') upon chaotic matter. Physical things thus only participate to some degree in the perfection of Plato's paradigmatic Forms.  Aristotle, on the other hand, holds that substantial forms actualize the potency of prime matter made receptive by agents of change. The chick's substantial form actualizes prime matter that has been individualized into being a receptive potency for the ''chicken's'' substantial form by the hen and the rooster.

While the concept of substantial forms dominates [[ancient Greek philosophy]] and [[medieval philosophy]], it fell out of favor in modern philosophy.{{Citation needed|reason=Previous citation old, broken link|date=October 2024}}
Modern philosophy was changed by the discovery of nature's mathematical and mechanical laws. So, the idea of substantial forms was abandoned for a [[mechanism (philosophy)|mechanical]], or "bottom-up" theory of organization.<ref>[https://www.anselm.edu/sites/default/files/Documents/Institute%20of%20SA%20Studies/4.5.3.2c_51Hill.pdf Benjamin Hill.  Substantial Forms and the Rise of Modern Science]</ref> Each substance being in its nature fixed and determined, nothing is farther from the spirit of Aristotelianism or Scholasticism than a theory of [[evolution]] which would regard even the essences of things as products of change. However, such mechanistic treatments have been criticized by proponents of [[Neo-scholasticism|Neo-Scholasticism]] for merely denying the existence of certain kinds of substantial forms in favor of others (for example that of [[atom]]s) and not denying substantial forms as such.

==Articulation==

===Aristotelian forms===
{{main|Hylomorphism|Aristotle's biology}}
Responding to [[Plato]]'s [[Theory of Forms]], [[Aristotle]] was the first to distinguish between [[Matter (philosophy)|matter]] (''[[hyle]]'') and form (''morphe''). For Aristotle, matter is the undifferentiated primal element: it is rather ''that from which things develop'' than a [[thing in itself|''thing-in-itself'']]. The development of particular things from this germinal matter consists in differentiation, the acquiring of particular forms of which the knowable universe consists (cf. [[Formal cause]]). The perfection of the form of a thing is its [[entelechy]] in virtue of which it attains its fullest realization of function (''[[De anima]]'', ii. 2). Thus, the entelechy of the [[human body|body]] is the [[soul]]. The origin of the differentiation process is to be sought in a [[Unmoved mover|prime mover]], ''i.e.'' pure form entirely separate from all matter, eternal, unchangeable, operating not by its own activity but by the impulse which its own absolute existence excites in matter.<ref>{{EB1911|wstitle=Form}}</ref>

===Early adoption===
Aristotelian forms appear in [[medieval philosophy]].

Medieval theologians, newly exposed to Aristotle's philosophy, applied hylomorphism to Christianity, such as to the [[transubstantiation]] of the Eucharist's bread and wine to the body and blood of [[Jesus]]. Theologians such as [[Duns Scotus]] developed Christian applications of hylomorphism.

The Aristotelian conception of form was adopted by the [[Scholastics]], to whom, however, its origin in the observation of the physical universe was an entirely foreign idea. The most remarkable adaptation is probably that of [[Aquinas]], who distinguished the spiritual world with its subsistent forms (formae separatae) from the material with its inherent forms which exist only in combination with matter.

==Criticism==
[[René Descartes|Descartes]], referring to substantial forms, says:
<blockquote>They were introduced by philosophers solely to account for the proper action of natural things, of which they were supposed to be the principles and bases ... But no natural action at all can be explained by these substantial forms, since their defenders admit that they are occult, and that they do not understand them themselves. If they say that some action proceeds from a substantial form, it is as if they said it proceeds from something they do not understand; which explains nothing.<ref>Descartes. "Letter to Regius," January 1642, in Oeuvres de Descartes.</ref></blockquote>

[[John Locke]] criticised 'substantial forms' as ill-defined, stating that they "signify nothing"<ref>{{cite book |last1=Locke |first1=John |title=Of the Conduct of the Understanding |date=1825 |publisher=Baynes & Son |pages=57–8}}</ref> and that the supposition that "the same precise and internal constitution goes always with the same specific name, makes men forward to take those names for the representatives of those real essences".<ref>{{cite book |last1=Locke |first1=John |title=The Philosophical Works of John Locke Volume 2 |date=1892 |publisher=George Bell & Sons |page=106}}</ref>

[[Isaac Newton]] in his ''[[Philosophiæ Naturalis Principia Mathematica|Principia]]'' situates himself within the contemporary scientific movement which had "omit[ed] substantial forms and the occult qualities" and instead endeavoured to explain the world by empirical investigation and outlining of empirical regularities.<ref>{{cite journal |last1=Zilsel |first1=Edgar |title=The Genesis of the Concept of Physical Law |journal=[[The Philosophical Review]] |date=1942 |volume=51 |issue=3 |pages=245–279 |url=https://www.jstor.org/stable/2180906}}</ref>

==Response to criticism==
[[Gottfried Wilhelm Leibniz|Leibniz]] made efforts to return to forms. Substantial forms, in the strictest sense for Leibniz, are primitive active forces and are required for his metaphysics.<ref>Adams, Robert Merrihew. Leibniz: Determinist, Theist, Idealist, February 1999, pp. 308–341 (34)</ref><ref>[http://www.iep.utm.edu/l/leib-met.htm#SH9c Internet Encyclopedia of Philosophy]</ref> In the ''[[Discourse on Metaphysics]]'' (§10):
<blockquote>[...] the belief in substantial forms has a certain basis in fact, but that these forms effect no changes in the phenomena and must not be employed for the explanation of particular events.<ref>{{cite web|archive-url=https://web.archive.org/web/20020612043559/https://www.anselm.edu/homepage/dbanach/Leibniz-Discourse.htm#X|url=https://www.anselm.edu/homepage/dbanach/Leibniz-Discourse.htm#X|title=Discourse on Metaphysics|author=G W Leibniz|archive-date=12 June 2002}}</ref></blockquote>

==References==
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[[Category:Aristotelianism]]
[[Category:Metaphysical properties]]
[[Category:Philosophy of Aristotle]]
[[Category:Concepts in ancient Greek metaphysics]]