Substance

[gL.edu] This article gathers contributions by Frederic Marx, developed within the context of the Conceptual clarification about "Information, Knowledge and Philosophy", under the supervisión of J.M. Díaz Nafría.

The concept of substance has been a cornerstone when talking metaphysics, where most philosophers have had their share of ideas. Plato stated a division between the perfect, eternal Forms and their imperfect material projections, while Aristotle thought of substance as a combination of matter and form, resulting in a substratum, while distinguishing between individual entities and types.

Stoics and neoplatonists redefined substance with spirit and material dimensions. In the Middle Ages, Arabic Jewish and Latin scholasticism adapted Aristotelian and Neoplatonic ideas to theological debates, focusing on substance's relationship with essence and existence.

Early modern thinkers like Descartes, Locke, Berkeley, and Hume reexamined substance, criticizing its necessity, based on perception and cognition. Kant viewed substance as a mysterious yet necessary cognitive tool for continuity rather than a metaphysical entity.

Modern critiques, including bundle theory and process theory, reject static substance and propose dynamic relations to be more accurate, supported by quantum mechanics and field theory. Despite this, substance remains a vital concept for explaining persistence, identity, and causality, contemporary adaptations ensure its continued relevance.

Ancient Philosophy

Plato (left) and Aristotle

Plato

Plato’s theory of forms dictates two existential forms of existence:

• The intelligible Realm: the world of forms, containing only eternal, perfect and unchanging forms or ideals

• The sensible realm: the material world, forms here are only a distinct, imperfect projection of perfect forms

He argued that physical entities alone are not substances. Only when they take a similar shape or imitate perfect forms do they become substance, otherwise their transient nature disqualifies them from being part of foundational reality. As in a painting is beautiful because it currently participates in the form of “beauty”.

Aristotle

Different to Plato, Aristotle defined substance (ousia) systematically. Due to him not sharing Plato’s theory of ideas.

He distinguishes between primary substance and secondary substance. Primary substance refers to individual entities, such as a specific human or tree, which exist independently and are subject to change. While secondary substance refers to the species or type, like human or Plant. They are not first and proper beings (ousia prote) because they are necessary for categorizing primary substances which makes them dependent.

Aristotle’s hylomorphic theory asserts that substance consists of matter (hyle) and form (morphe). Together the matter’s underlying potentiality and the form’s actuality or essence make up the specific identity of an object.

Aristotle’s substance can be linked to his theory of causality, specifically the formal cause (what something is) and the material cause (what something is made of). Substances are not static, but subject to change while maintaining some continuity. Essential or substantial properties defining an object remain, they give something its essence, while propria, are necessary to the object without altering its function or use.

The material cause of a Substance is the matter an object is composed of, while the formal cause provides shape or essence. While a lot of things are made of wood, a chair has a very distinctive form and use, resulting in a more specific substance than just pieces of wood. If overtime the chair got old and fell apart, it has no more sitting purpose (which in the case of a chair is its defining characteristic), therefore does not qualify as a chair anymore, while still consisting of wood. The theory of causality helps explain Aristotle’s view of potentiality (matter) and actuality (form), how substances are, change their form, or purpose.

Ultimately Aristotle understood Substance as the foundation of existence, without which no other categorization, such as individual properties, relation or quantity, could take place.

Stoicism

Stoics rejected Plato’s definition of substance and instead believed that all beings, not all things, are made from matter infused with a soul or spirit (pneuma). They developed categories different from Aristotle’s based on the ideas of Anaxagoras, building four categories:

• Substance (ousia): the formless matter;
• Quality (pneuma): the way matter is structured to form an individual object by the active principle;
• Dispositions: characteristics present or not present in an object, such as size, shape, action or state, in relation to other objects
• the active principle: a force to govern nature, comparable to the modern laws of physics we know today

Through these categories substance was better embedded in the stoic belief system. They emphasize a unity between matter and spirit, stating a strong contrast to Aristotelian metaphysics.

Neoplatonism

Neoplatonists argue that properties which we conceive through our senses are three spiritual principals or hyopstases:

• Soul
• Intellect
• the One: monad/absolute; the most basic or original substance

and build on Plato's idea of substance, via introducing a hierarchy

1. the One: Beyond substance and being

2. Nous (intellect): the realm of "true" substance, where perfect forms reside;

3. Soul (Psyche): a dynamic substance that connects the material world to higher realities

4. Material world: The lowest level of substance, characterized by imperfection and distance from "the One"

in Neoplatonism, the One transcends substance. It is the source of all existence and cannot be classified as substance.

Middle Ages

Early Christian theology also employs the ontological concept of substance, albeit often in ways that deviate from established systematic frameworks, particularly when it is used to protect mysteries of faith, such as trinity or transubstantiation, the transformation of wine and bread into the blood and body of Christ, from overly simplistic ontological interpretations.

Arabic, Jewish and Latin Philosophers integrated ancient terminology and concepts related to the notion of substance.

The Arabic scholasticism, heavily influenced by Aristotle and later Neoplatonism, had a big part in the medieval discussion around substance, focusing on the relationship of substance and essence and the distinction of essential (essence, mahiyyah) and existential (existence, wujud). This distinction shaped later debates on whether substance could exist independently of its essence and had an influence on both Jewish and Latin scholasticism.

The Jewish Scholasticism also made use of Aristotle’s framework while developing their own, which in the 14^th and 15^th century integrated Aristotle’s philosophy with Jewish theology. Focusing on logic, individuation and the concept of future contingents. A notable mind includes Maimonides who integrated Aristotle’s with Jewish theology focusing on Gods attributes and unity.

Latin Scholasticism saw the nature of substance with a more realistic and normalistic view and debated whether all universals had independent existence or were merely mental constructs. Thomas Aquinas for example emphasized the unity of form and matter while addressing theological concerns like the nature of the soul.

Early modern Philosophy

René Descartes

Descartes viewed substance as something that exists independently, which is reliant on nothing to exist. For him, only God qualifies as a truly independent substance, therefore all substance is reliant on God as a substratum. He differentiated between two basic types of created substances: mind (res cogitans), such as thought, and matter (res extensa), defined by an extension in space. Descartes' substance dualism insists that mind and matter are entirely distinct, the mind can not extend in space while matter can’t think, and not reliant on each other’s existence for their own. This separation goes hand in hand with his God centered metaphysical system.

John Locke

Viewing the issues in contemporary philosophy of substance, Locke’s influence is considered almost as important as Aristotle’s due to his definition which contains two conceptions of substance: the “notion of a pure substance in general” and the “ideas of particular sorts of substance”.

Pure substance in general possesses properties, or in Locke’s terms: qualities, which must belong to something and couldn’t exist without being assigned to substratum. He disagreed with Aristotle’s category of substantial form on what said substratum is, and went with what was left, something which possesses no properties of its own besides being the owner or support of all properties.

John Locke, by Sir Godfrey Kneller, 1704

He himself was often not quite sure how he felt about his definition of substance, describing his dilemma with “something I know not what” due to the fact, that human observability is limited to the senses we possess and therefore something’s properties. For example, everything that makes an apple an apple, are its apple like properties (e.g. taste, texture or color). To clarify: Locke was confident in the necessity that substance poses to observability, he just questioned if there is any knowledge to gain about something stripped of every last quality, something that can not be perceived. He earned quite some criticism for his work. Berkeley was convinced that there is no need to categorize anything other than qualities due to the unperceivable nature of substance (more on Berkeley down below). Locke’s work is a pinpoint of the transition between scholasticism and modern philosophy, while scholastics thought of substance in metaphysical terms, he concentrated on a more physiological approach, about how humans can perceive something beyond their sensory perception.

George Berkeley

He considered material substance as an unnecessary abstraction. He believed that to exist is to be perceived (esse est percipi), so everything that is, is either an idea or a mind comprehending it, therefore, and contrary to Locke, if something is stripped of all of its properties and can not be perceived by the human senses, it does not exist. He found the idea of substance as a substratum without observable qualities abstract and illogical. His categorization is based on two kinds of perceiving minds:

• the finite mind, e.g. humans;
• infinite mind, God.

God ensures continuity if finite minds are not actively perceiving something. Despite God also playing a big role in Descartes substance dualism, Berkeley accepted the mind as “substance” and saw matter as unnecessary.

Berkeley’s theory of immaterialism/idealism states that objects are merely a combination of ideas perceived by the mind. For example, a bench exists because its being perceived, if not by humans, it is by God, while the color of the bench only exists as sensory experience in the individual mind. This position evades the need for Aristotle’s substratum.

David Hume

Hume rejected the idea of substance, arguing that all we know are impressions and ideas. Substance, as an underlying entity, is not observable and therefore not necessary. He famously stated, that “The idea of a substance […] is nothing but a collection of simple ideas, that are united by the imagination”. His critique shifted the focus from metaphysical speculation to observable phenomena, laying the groundwork for bundle theory and many more.

Immanuel Kant, by Johann Gottlieb Becker, 1768

Immanuel Kant

In Kant’s first analogy of experience, he determined substance as necessary for the continuity of experience, where in his opinion substance makes up the permanent part. If substance was not permanent, its changes would, in an otherwise changing world, lack coherence.

Contrary to Locke and Aristotle, he did not believe in an unknowable underlying substratum objected to properties, but in a mental construct, necessary for cognition yet not a metaphysical entity. Kant’s work is relevant to this day in the discussion if substance remains a useful category in metaphysics, he connected empirical observation with metaphysical speculation.

Historical summary on the debate about substance theory

Substance has been a cornerstone of metaphysics for centuries, as well as a hot topic for many. Most philosophers have reflected on this subject, so naturally there is no shortage of schools of thought, among which criticisms abound, ranging from lack of coherence to necessity to empirical substantiation.

One of the most popular critiques is the vagueness of the concept, as some think substance is not easily definable. Most in support of substance describe it as a blank slate for properties, but this definition leaves much to be desired. Locke addressed this issue from both perspectives with his “something I know not what” statement, which refers to the imperceptibility of substance. The fact that to the human senses, it is undetectable, jet a necessary concept. Hume did not agree with Locke on the necessity of substance. His empirical skepticism proposes that there is no underlying substance, due to neither perception, nor reason revealing anything beyond observable qualities in objects.

Modern Critiques

Modern interpretations often classify substance as an unnecessarily complex theory. Hume & Russell’s bundle theory states that there are merely collections or bundles of properties, no underlying substance. Supporters of this theory argue that e.g. an apple is not consistent of a substratum which is host to properties like sweetness or its round shape, instead an apple is its sweetness and round shape. The emergence of new objects by the combination of others, or unity problem, is explained by relations between present properties in the combined ingredients, resulting in the appearance of a cohesive object.

Whitehead’s process theory observes reality as far too dynamic, for an unchangeable substratum. Instead, supporters view the world as prone to change where entities are temporary manifestations of an ongoing process or event. This can be visualized by observing a deciduous tree year-round. While most of the time it will be green and voluminous, in fall and winter it will go through fundamental changes in some of its most recognizable properties, jet remain the very same thing it once was and will be again. This theory can also be applied to the probabilistic nature of electrons and their interactions within quantum fields, this argument is used in modern interpretations of substance till the present day, more on this below.

Developments in quantum mechanics and field theory have also challenged substance as a stable, independent entity. Instead, reality is more and more understood to be composed of fields, interactions, and probabilities, not leaving much room for the ancient metaphysical substance definition as a solid substratum. Descartes’ definition of substance being a “extension in space”, is, because of new knowledge on matter and atoms, an oversimplification. As we now know, the atoms that make up all matter in our universe are mostly empty, with the exception of the core or nucleus in the middle, this implies that all objects are mostly empty space. For example, the radius of a hydrogen atoms nucleus only takes up less than 1% of its total radius, roughly 1:10.000 to be more precise, like a pea in a sphere with a 1km diameter. The only other component of an atom, electrons, are not solid balls, but probabilistic clouds whose position is impossible to pinpoint while also being aware of the state that they are in at one moment. The Cartesian “extension in space” is misguided through the illusion of solidity through atomic bonds, while the vast majority of everything physical remains empty space.

Arguments in support of substance

Kant

Kant’s idea of substance as a category of understanding preserves its utility as an explanatory substratum, while avoiding metaphysical speculation. For him, substance is immensely helpful for structuring experience, even if perceiving it is not possible.

Explaining persistence and identity

Substance is still a valid concept in regard to explaining persistence and identity. A stable substratum helps to grasp how objects with everchanging properties maintain their identity, e.g. an rotten apple that has lost most typical apple-like qualities (like the specific taste, the color or the shape) while remaining an apple. This concept also applies to personal identity, as it demonstrates the self as an enduring entity, crucial for discussions in ethics and psychology.

Contemporary metaphysicians, such as E.J. Lowe, argue that substance provides the ontological foundation for properties and events. Substance theory offers a compelling way to account for causation. Substances are seen as bearers of causal powers, enabling the interaction of objects in a coherent and predictable manner. Without substances, explaining the unity of properties and their causal relationships becomes challenging.

Modern scientific adoption

The theory of substance is, even after years of scientific development, not obsolete. For instance, some use quantum states or fields as definition for substance, adapting the concept to our modern view of the world, aligning with process ontology.