Hylomorphism (Greek ὑλο- hylo-, "wood, matter" + -morphism < Greek μορφή, morphē, "form") is the philosophical theory, originating with Socrates, which conceptually identifies substance as matter and form. More exactly, substances are conceived as forms inhering in matter.
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 Stoics rejected the ideas of both Socrates and Aristotle, believing only in matter. They developed their own theory of categories, largely in order to avoid reference to incorporeal form. Their triumph over both the Academy and the Lyceum was very likely due to their rejection of the ideas of their predecessors.
Plotinus revived the idea of the ideal form in Neoplatonism. He understood matter to be empty space, or a pure possibility of being. The acceptance of Plotinus by Saint Augustine as the best of the pagan philosophers marks the introduction of hylomorphism into Christian thought. Subsequently, the Theology of Aristotle, a translation of Plotinus' Six Enneads into Arabic was essential to the work of Islamic philosophers. Thomas Aquinas' ideas, building on Islamic thought, introduced Aristotle's version of hylomorphism into Western thought.
Hylomorphism is the philosophical theory, originating with Plato, perhaps earlier, which theorizes that substance is composed of matter and form, which are not to be understood as any element, atom, part or particle. Substance is not a mixture, solution, colloid, amalgam, chemical or physical unity of matter and form. Instead the two are composed homogeneously together such that no matter exists without form or form without matter. Pure matter and pure form can never be perceived. They can only be comprehended by intellect, which is able to abstract, or "take away" the form from the matter and vice versa in the mind only.
There are no instances of matter and form in the world of modern physics and chemistry , only instances of substance. They cannot be studied by means of any instrument or experiment whatever , and therefore their existence is open to question, as modern science only believes what it can verify experimentally. Substance, however, can be verified experimentally. A close analogy to this epistemological position in physics is perhaps the nature of the electron, which explains properties of atoms, but cannot be experimentally verified (Heisenberg uncertainty principle) and therefore does not exist. Particle physicists view it as a probability function without being able to state what that means in physical reality .
Similarly the nature of matter and form cannot be explained . They have no nature. Instead they explain the overall characteristics of substance: multiplicity and change. An analogy in the physical world might be a colored light beam being formed from two primary colored light beams. Another is the location of an object in "space", which combines matter and space.
Two major views of the reality of matter and form were formulated by the ancients. In Platonic idealism or the theory of the ideas forms as seen in substance are not real, but are the projections of real forms, which exist in a world of forms, where man before he was born perceived and learned them. Someday man will awaken again and see the forms rather than the shadows. The shadows are formed from the projection of the forms onto space, which is real. It became Aristotelian matter. Aristotle held that matter and form are both real and exist where they are seen in substance. His view is therefore called Aristotelian realism.
The latter must appear paradoxical to modernists: matter and form do not exist apart from each other but only together. A substance is a unity and yet its matter and form are really distinct although they cannot by any means be separated, as they have a natural affinity for each other. Matter and form are not imaginary or concepts only, they really exist, but not with their own existence. The existence is that of the substance.
Due to the historical magnitude of its founders, hylomorphism was the western world's major world view. It became mediaeval because it was classical without lapse or other interruption. Certain problems concerning the relationship of existence to substance continued. These were solved finally by Saint Thomas Aquinas, often on that account termed the last of the ancient philosophers. His solutions became incorporated into the then Christian church as dogma. Subsequent to the schism between Catholicism and Protestantism the Catholics retained the dogma but the Protestants came to reject it to varying degrees and finally not to understand it at all.
The form of a thing gives that thing its nature. Totally unformed matter — "primary matter" — is pure potential without any actual properties; thus, it's only a concept and can't actually exist in the real world. The most basic forms are the forms of the elements. These forms organize primary matter into the four classical elements — earth, fire, air, and water. These elements are indivisible and the simplest things in existence. The elements are then organized by more complex forms into a multitude of things. For example, the forms of flesh and bone organize the elements into flesh and bones; the forms of various organs organize flesh and bones into various organs; and the form of humanity organizes various organs into a human being.
According to Aristotle, the "soul" of a living being is its form, its organization. A living being is a collection of matter that is organized so that its organization is self-sustaining. By defining "soul" as the organization of a living body, Aristotle denies the possibility of a soul that can survive the death of the body. At most, only the pure intellect, devoid of personality, can survive according to Aristotle's theory.
According to Aristotle, nature in inherently purposeful. Matter exists for the sake of form; potential exists to be actualized. Bricks, mortar, and beams exist for the sake of a house. The parts of the human body exist for the sake of the human body. Moreover, once a thing has fully gained its form, we can say that it ought to exercise the functions that its form gives it. For example, the form of a snake's body gives a snake the ability to slither, so a snake ought to slither. The farther a being deviates from its form, the less it succeeds in satisfying its purpose. Aristotle presents a teleological world — a world in which things have objective purposes. In particular, a thing's purpose is to fulfill the functions that its form gives it.
In contrast, according to hylomorphism, the term "oak tree" corresponds to an objective reality with causal powers. When an acorn grows into an oak tree, it's "striving" after the form of an oak tree. The meaning of the term "oak tree" exists as an objective goal that draws matter toward it.
Some modern philosophers, such as Patrick Suppes in Probabilistic Metaphysics, argue that hylomorphism offers a better conceptual framework for the Standard Model of particle physics than purely mechanistic versions of atomism.
Many medieval Jewish, Christian, and Muslim theologians, particularly the Thomist theologians, applied Aristotelian notions of an Unmoved Mover to religious notions of God.
This posed a problem for the medieval Christian philosophers. Christian doctrine seemed to state that humans have individual souls that can continue to exist individually after death. Thus, medieval philosophers sympathetic toward Aristotle faced a dilemma. On one hand, they could accept Aristotle's definition of the soul as pure form, but at the expense of having to explain how the individual soul could survive death. On the other hand, they could define the soul as a substance made of both form and matter, but at the expense of contradicting Aristotle. Some medieval thinkers, such as Saint Thomas Aquinas, agreed with Aristotle that the soul is pure form. Others, such as Saint Bonaventure, argued that the human soul must consist of both form and matter: thus, it must contain some kind of "spiritual matter", but still be able to act upon the body's corporeal matter as its form.
Others, such as Bonaventure, argued that angels, like everything else, must consist of both matter and form. Bonaventure knew of Aquinas's idea "that each angel constitutes a single species", but he thought that one should accept "so strange a theory" only if Scripture explicitly supported it or if logic absolutely demanded it. Unlike Aquinas, Bonaventure concluded that angels share a common angelic form. According to Aristotle, different individuals can have the same form only if they're different pieces of matter. Thus, according to Bonaventure, angels must contain "spiritual matter" as well as form.
However, Bonaventure defines matter more abstractly: for him, "matter" is the principle in each thing that makes it a particular thing: it's what makes an angel this particular angel, in contrast to the form, which is angelhood-in-general. In itself, Bonaventure's matter is neither corporeal nor spiritual: it becomes corporeal if joined with the form of a corporeal being, and spiritual if joined with the form of a spiritual being.