A problem of definitions: on the realist definition of substance
The word “substance,” like “matter,” is another of those words that is used differently by empirical scientists and realists.
In empirical science the word substance means anything that has a unique chemical formula. Helium gas would be a substance and its chemical formula would be simply He. Hydrogen gas would be a substance and its chemical formula would be H2, since the natural form of hydrogen is that of a diatomic molecule. Water would be a substance and its chemical formula would be H2O. If water is in the liquid form these molecules are connected in a strong but fluid manner through interactions known as hydrogen bonds. Table salt is a substance with the chemical formula of NaCl. It exists in a crystalline ionic structure rather than as individual salt molecules. Mixtures are not themselves substances but rather are composed of two or more combined substances not chemically joined. So from the perspective of an empirical scientist, a very complex thing such as an animal like a rabbit is an intricate arrangement of various organic and inorganic substances. It would be rather odd to consider the rabbit itself as a substance.
Realists view the substance as that which “stands under” (from the Latin sub stare) the thing, accounting for its unity and supporting its “accidents,” which are the characteristics intrinsic to a thing (its quantity, including how it is extended throughout space and its qualities) as well as how it exists in the world (relation, action, reception, place, orientation, environment, and time). We are able to sense the accidents of a thing but the substance is something that is only grasped by the intellect. Strictly speaking we see a tree’s size and color, hear the wind rustling its leaves, feel the texture of its trunk, and smell its sap, all of which are accidents. We do not experience the substance of the tree with our senses: rather we intellectually grasp that what we see, hear, feel, and smell is a particular tree, with a unity that supports the diversity of the accidents that we can experience.
Strictly speaking a “substance is that reality to whose essence or nature it is proper to be by itself and not in another subject.” Alvira, Clavell, Melendo, Metaphysics 46. In this definition there is a sense of unity to something with substantial existence. But this unity does not mean autonomy, in the sense of something not being dependent or needing something else to exist. Id. at 47. Reality is not the sum total of individual substances considered relative to each other. Reality – being (esse), what exists – is more like a great “explosion” of esse received by particular essences in such a way that particular substances exist in a great web of interconnected relationships in which each created thing is radically dependent. This dependence is fundamentally a dependence on God as creator, who continues to simultaneously hold creation in existence, and does so through a network of causes, many of which are intelligible to us.
No substance = no such thing as a rabbit
Like an empirical scientist, a realist could also think of a particular body of water or a sample of table salt in terms of substance, but something different is meant. The empirical scientist means that the body of water is a substance because it is one compound, specifically H2O. The realist is more likely to think of a particular body of water, say Walden Pond, as having an imperfect unity analogous to the substantial unity in a living thing like a rabbit. And if we think of a stream flowing into the pond and another exiting, providing a continuous connection to a river and eventually to the ocean, the problem of identifying what constitutes a specific body of water can be a difficult one for the realist.
But as the thing in question becomes more complex and of a higher order of being, the notion of substance employed by the realist becomes clearer. The realist will see an organism, such as a rabbit, as possessing substantial existence in a more complete way. The rabbit has a unity in that it is one living subject that actively seeks certain ends, with different biological systems all supporting the organism in an integrated and coordinated way. When the rabbit eats grass some of the grass consumed actually undergoes “a substantial change” and becomes part of the rabbit. A living organism shows substantial existence in a more perfect way than inanimate natural objects. Thus what to the empirical scientist is not identified as a substance at all, but rather as many substances, to the realist is a better example of what a substance is, since unity is clearer in a living thing.
Well, perhaps the reader is wondering why this is important. Sure, it is clear from the above that empirical science and realist philosophy use a technical vocabulary word, “substance,” in distinct ways. So what? Is this merely of “academic” interest?
Actually, there is quite a bit at stake here. There is nothing wrong about using a word to mean something that has a specific molecular or ionic structure, something that can be identified by its chemical formula. It may be a bit unfortunate that the word chosen for this purpose is “substance” since it has classically meant so much more and still retains some of its classical meaning in common parlance. Human language in general assumes that it is fitting to speak of things as having what the realist would call substantial existence. We do not say “the substance of the rabbit was eaten by the substance of the wolf, ceasing to be a rabbit and becoming part of the wolf.” But when we say the wolf ate the rabbit our language assumes the classical meaning of substance in as much as we are calling the rabbit a rabbit and the wolf a wolf.
What would be tragic is if the classical meaning of the word “substance” is obscured – not that this meaning necessarily has to accompany the word “substance” – but that we become confused about the concept of things having substantial existence. This is clear if we take such a reduction to its logical extreme. Let’s suppose, for the sake of illustration, that any substantial existence in the classical sense is just an illusion. In other words, nothing is really a distinct thing, a distinct subject. At most all we can say is that human language assumes, or has assumed up to this point in history, substantial existence as a convenient way to talk about the way it appears than some things are actually substances. If such an assumption were true, the rabbit we were considering would not really be a rabbit. To call it a rabbit would be to assume that there is a unified subject actually existing that is distinct from the rest of existence such that it can be identified as a rabbit while other things around it can be identified as non-rabbit. But if all that is really there are configurations of various modular construction units, considered as particles or as “energy packets” or whatever, then there really is nothing other than a giant cosmic soup of such modules. It is ultimately meaningless to speak of a “rabbit” as the very boundary between the body that you are attempting to define as a rabbit and the cosmos is obscure. Furthermore, and on the level of the cosmic soup, there is no clear demarcation between the atoms that make up the so-called rabbit and those similar atoms that make up the so-called adjacent grass. There is no real unity to either the rabbit or the grass, just a continual Heraclitian flux between what we refer to as a rabbit and as grass and everything else as well. In other words if the only meaning of substantial existence is being of a certain chemical configuration, then human language and thought falls apart. What is a mountain? A river? A spider? A bear? A human person? Despite whatever words are used, if the classical meaning of the word substance is lost we will necessarily end up literally without the ability to think rationally.
A breakdown in the meaning contained in the classical use of the word substance would lead to a violation of the principle of non-contradiction, which states that nothing can both be and not be at the same time and in the same respect. If the classical meaning of substance is lost then we lose the ability to consider reality as having a level of intelligibility such that the principle of non-contradiction could apply. If there are no substances then there are really not any subjects of which we can predicate particulars. Something cannot be thought to be or not be in a particular way because it is not clear that it is a “something” in the first place. If the only constant is change, as Heraclitus taught, then there can be no subject that contains enough stability to be said to be changing.
Well, these are crazy ideas to which no sane person would adhere, except as a sophisticated mental game. But softer versions of this perspective do have an impact on people today, both as individuals and as part of the collective understanding we share as manifest in our use of language. The problem is not that students and empirical scientists study atoms or other aspects of reality on the microscopic level; reality has intelligibility on this level and it is good to study it. The problem is if someone considers objective reality as only a complex mechanical configuration of particles or other modular construction units. The problem is a reduction of the scope of human reason to only consider one aspect of reality as objective, a problem that is mostly an absence of a broader and more open minded perspective, specifically a metaphysical perspective, a perspective that should be present as well.