Editing Hylomorphism (section)

===Medieval modifications===
Thomas Aquinas emphasized the act/potency understanding of form/matter whereby form activates the potency of matter and existence activates souls. The angels are accordingly composites of esse (potentiality) and [[Actus essendi|existence]] (actuality) that activates immaterial souls, while God alone is per se existence, pure act without any potencies.

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

Aristotle's texts on the agent intellect have given rise to diverse interpretations. Some following [[Averroes]] (Ibn Rushd 1126–1198) argue that Aristotle equated the active intellect with a divine being who infuses concepts into the passive intellect to aid human understanding. Others following Aquinas (1225–74) argue that the Neoplatonic interpretation is a mistake: the active intellect is actually part of the human soul.

====Substantial form, accidental form, and prime matter====
{{See also|Substantial form}}
Medieval philosophers who used Aristotelian concepts frequently distinguished between [[substantial form]]s and accidental forms. A substance necessarily possesses at least one substantial form. It may also possess a variety of accidental forms. For Aristotle, a "substance" (''ousia'') is an individual thing—for example, an individual man or an individual horse.<ref>''Categories'' 2a12-14</ref> Within every physical substance, the substantial form determines what kind of thing the physical substance is by actualizing prime matter as individualized by the causes of that thing's coming to be. For instance, the chick comes to be when the substantial form of chickens actualizes the hen's egg and that actualization is possible insofar as that egg is in potency to being actualized both as a chicken due to the receptivity of its prime matter to the substantial form of chickens and into a chick with certain colored feathers due to the individualization of the egg given by its parents. So while the individualized matter determines individualized properties, the substantial form determines essential properties. The substantial form of substance S consists of S's essence and its essential properties (the properties that S needs in order to be the kind of substance that S is<ref>Cross 34</ref><ref name="Kenny 24">Kenny 24</ref>). Substantial change destroys the ability of a substantial form to actualize individualized prime matter without affecting prime matter's ability to be actualized by a new substantial form.<ref>Leftow 136-37</ref> When the wolf eats the chick, the chick's rearranged matter becomes part of the wolf and animated by the wolf's substantial form.

In contrast, S's accidental forms are S's non-essential properties,<ref>Cross 94</ref> properties that S can lose or gain without changing into a different kind of substance.<ref name="Kenny 24"/> The chick can lose its feathers due to parasites without ceasing to be an individual chicken.

====Plurality vs. unity of substantial form====
Many medieval theologians and philosophers followed Aristotle in seeing a living being's soul as that being's form—specifically, its substantial form. However, they disagreed about whether X's soul is X's ''only'' substantial form. Some medieval thinkers argued that X's soul is X's only substantial form animating the entire body of X.<ref>Kenny 26</ref> In contrast, other medieval thinkers argued that a living being contains at least two substantial forms—(1) the shape and structure of its body, and (2) its soul, which makes its body alive.<ref>Cross 70</ref>

====Thomistic hylomorphism<!--Linked from 'Thomas Aquinas'-->====
{{Thomism}}
[[Thomas Aquinas]] claimed that X's soul was X's only [[substantial form]], although X also had numerous accidental forms that accounted for X's nonessential features.<ref name="ReferenceB">Stump, "Resurrection, Reassembly, and Reconstitution: Aquinas on the Soul" 161.</ref><ref>Stump, "Resurrection, Reassembly, and Reconstitution: Aquinas on the Soul" 165</ref> Aquinas defined a substantial form as that which makes X's matter constitute X, which in the case of a human being is also able to transcend the limitations of matter and establish both the [[reason|rational capacity]]<ref>Leftow, "Soul, Mind, and Brain" 397.</ref> and natural immortality of human beings. Nevertheless, Aquinas did not claim that human persons were their disembodied souls because the human soul is essentially a substantial form activating matter into the body. He held that a proper human being is a composite of the rational soul and matter (both prime matter and individualized matter).<ref>Eberl 340</ref><ref>Eberl 341</ref> So a soul separated from its body does not become an angel but retains its orientation to animate matter, while a corpse from which the soul has departed is not actually or potentially a human being.<ref name="ReferenceB"/>

[[Eleonore Stump]] describes Aquinas' theory of the soul in terms of "configuration". The body is matter that is "configured", i.e. structured, while the soul is a "configured configurer". In other words, the soul is itself a configured thing, but it also configures the body.<ref>Stump, "Non-Cartesian Substance Dualism and Materialism without Reductionism" 514.</ref>  A dead body is merely matter that was once configured by the soul. It does not possess the configuring capacity of a human being.

Aquinas believed that rational capacity was a property of the soul alone, not of any bodily organ.<ref>Stump,"Non-Cartesian Substance Dualism and Materialism without Reductionism" 512.</ref> However, he did believe that the brain had some basic cognitive function.<ref>Stump, "Non-Cartesian Substance Dualism and Materialism without Reductionism" 512.</ref> Aquinas’ attribution of rational capacity to the immaterial soul allowed him to claim that disembodied souls could retain their rational capacity as his identification of the soul's individual act of existence allowed him to claim that personal immortality is natural for human beings. Aquinas was also adamant that disembodied souls were in an unnatural state<ref>Stump, "Non-Cartesian Substance Dualism and Materialism without Reductionism" 519.</ref> and that the perfection of heaven includes God miraculously enabling the soul to function once again as a substantial form by reanimating matter into a living body as promised by the doctrine of the resurrection of the dead.