Introduction:
The term "substance" refers to that which underlies and supports its attributes and properties. The term "attribute" refers to that which is ascribed to a thing. Hence an attribute is that which is proper to a thing, its essential property. Loosely, it refers to a quality or characteristic of a thing. In metaphysics an attribute is what is indespensible to a spiritual and physical substance; or that which expresses the nature of a thing; or that without which a thing is unthinkable. As such, an attribute implies necessarily a relation to some substance of which it is an aspect or an element in its conception. Attributes are said to inhere in their substance.
History:
Plato used the term "substance" to signify that which is sought by philosophicak investigation of the primary being of things. The Platonic dialectic method was aimed at a knowledge of the essential nature (ousia) of things. It sought to find those elements common to all things of certain kind and capture them in its definition.
Aristotle was also primarily concerned with the investigation of the being of things, but from the standpoint of generation or change. But only individual things are generated or changed. Hence, for him, substance was primarily the individual: a "this" which, in contrast with the universal, is unique to the individual. The substance of the individual Aristotle called primary substance. Plato's substance, the universal essence of a thing, Aristotle called secondary substance.
Thomas Aquinas accepted Aristotle's analysis of substance and attributes (and properties). Aquinas brought into the discussion of substance the distinction between essence and existence. Primary substance is characterized by existence and secondary substance is characterized by essence. So in Medieval philosophy primary substance came to be viewed as existence as added to essence; substance is an existing essence.
Duns Scotus also accepted Aristotle's analysis of substance and attributes. But he substituted the term haecceitas ("thisness"), and the term "entitas singular" ("individual being") for primary substance, arguing that by virtue of the haecceitas the being in question is this being.
William of Occham restricted the use of the term "substance" to primary substance alone, thus establishing the modern usage, and thus reducing the complexity of the analysis.
Descartes redefined substance as any subject containing "a property, quality, or attribute." Following the medieval stress on independence, he also held that substance to be "that which exist by itself" without the aid of anything else. Substance does not depend upon anything else, whereas attributes always depend on substance. On the basis of this definition he distinguished between finite and infinite substance, and pointed out that God alone is an infinite substance. Finite substances are of two kinds: mind is thinking substance and matter is extended substance.
Spinoza simply drew the logical conclusion of Descartes' definition of substance. If God is only infinite substance and truly self-existent, that is, that which exist by itself, then there can be only one substance, God Himself, and any finite substance, mind or matter, must be simply a mode of this one infinite substance. Spinoza rejected the Cartesian concept of finite substance, leaving only the infinite substance. According to Spinoza finite substance is a contradiction in terms. Spinoza further replaced the Aristotelian distinction between substance and accident with that between substance and mode. "By substance, I understand that which is in itself and is conceived through itself; in other words, that, the conception of which does not need the conception of another thing from which it must be formed." (Ethics, Def. III). Substance is thus ultimate being, self-caused or from itself (a se), and so absolutely independent being, owing its being to itself, and eternally self-sustaining. It is in itself (in se), and all things are within it.
Substance is one and there can be but one substance; God is this substance. Spinoza, rejecting the idea of finite substance, necessarily rejects the possibility of a plurality of substances. The attributes of the one substance are plural and are constitutive. But the plurality of attributes implied that substance as such cannot be understood by way of any one attribute or by way of several.
Leibniz who also started with Descartes's definition of substance as a self-existent subject found that reality is composed of many simple substances, which he called monads, their self-existence guaranteed by their character as non-extended centers of force.
Locke also redefined substance as the underlying substratum of change. His conception followed the genealogy of the word more closely than any other philosopher. As an empiricist he pointed out that while we can know the qualities which are embedded in the substratum, substance remained a "something I know not what." Similarly, he pointed out that our knowledge extends only to nominal essence of the thing. Even so Locke does not doubt that in each case a subject of change and a real essence do exist.
Berkeley, pushing Locke's point a bit further, denied the existence of the underlying substratum. He also denied that the perceptions of our senses are of the qualities of a substance. All we know are perceptions and ourselves. There are spiritual substances, myself, other selves, and God, of which we have no perceptions.
Hume pushed Berkeley's analysis of Locke's thought to its final step. If all we know is our perceptions and not the cause of them, then we cannot know any substance, since we have no perception of them. Thus he denied the existence of all substances, not only the material substances that Berkeley had eliminated, but also spiritual substances.
Kant regarded both substance and attributes (and accidents) as a synthetic apiori concepts derived from categorial judgments, that is, from the subject-predicate form of judgments. Whether they refer to anything in the external world is not known. The object-in-itself is unknowable.
The philosophical movement known as Phenomenalism attempts to construct a view of reality in the absence of the concept of substance. For example, one member of the movement substituted for the concept of substance the idea of a relative stable complex of sense qualities.
Russell and Whitehead attacked the concept of substance by denying the ultimacy of the subject-predicate form of propositions. Russell attempted to develop a view of the world without the use of substances called logical atomism; the world consists of atomic facts, and these can be represented by elementary propositions. Later he developed an ontology that he called neutral monism; the world is neither mental or material, but is composed of some neutral stuff, which, when organized according to the law of physics, yeilds physical objects, and, when organized according to the laws of psychology, yeilds minds. Whitehead replaced the substance-attribute ontology with an event ontology.
