Philosophy of Nature: III. The Four Causes
A: Material Cause
1. Prime Matter: Principle of potency for substantial change
As we saw when considering the problem of change, not only do substances undergo changes in accidents (apples change from green to red), but substances themselves change into others (wood changes into smoke and ash). And as a substance underlies and endures through the changes of its accidents, so there is something that underlies and endures through the substantial changes. Since it seems that any substance might potentially (eventually and ultimately) change into any other kind of substance (see below), Aristotle recognized that there is an ultimate stuff or substrate that grounds the radical potency of everything (eventually and theoretically) to turn into anything else. Dung becomes a worm, which becomes a bird, the bird a cat, the cat a coyote, the coyote a grizzly, which leaves his dung again, and the cycle repeats. And since Aristotle calls whatever is the bearer of potency the ‘matter’ in any change, this ultimate stuff is called ‘prime matter.’
However, that matter which is understood without any form and privation, but is the subject to form and privation, is called ‘prime matter’ because of the fact that before it there is no other matter. This is also called hyle. Also, because every definition and all knowledge come through form, prime matter cannot be known or defined in itself but only through some comparison. Thus, it might be said that prime matter is that which is related to all forms and privations, just as bronze [is related] to the statue and the shapeless; and this is called first simply speaking (simpliciter).[1]
Prime matter is what persists through the change of one substance into another, that underlies both substantial forms, and that is potentially both of them. As we will consider more below, substantial forms define and specify what each thing is before or after the change. Likewise, what underlies each substance and what persists through such changes is prime matter, the principle of potency to be an actual substance in a fundamental sense.
Prime matter, considered (abstractly) just by itself, is without any determination but is mere potentiality as such. This is not to say that prime matter is ever the immediate and direct subject of a change on which any actual agent acts. It exists only in actual determinate things as the radical potency to undergo limitless changes.
It should be known that, although prime matter does not have in its definition any form or privation (just as, in the notion of bronze there is neither shaped nor shapeless), nevertheless, matter is never completely devoid of form and privation: sometimes it is under one form and sometimes under another. It can never exist, however, by itself. For, since it does not have any form in its definition, it cannot have existence in act, since existence in act is only from a form. Rather, it exists only in potency. Therefore, whatever exists in act cannot be called prime matter.[2]
Prime matter is only and always found with some substantial form that gives it determination. Yet, although it never exists in and of itself, prime matter is real; it is a real principle of change. It is the real potency that every material thing has to undergo an indefinite amount of change.
We should not, therefore, say that prime matter is the simplest bodies of the material sublunary world; the four elements, earth, air, fire and water, themselves contain contraries and can be transmuted into one another. But if they change, then they presuppose composition of potentiality and act. Air, for instance, is air, but can become fire. It has the form or actuality of air, but it also has the potentiality of becoming fire. But it is logically necessary to presuppose, prior to the potentiality of becoming fire or any other particular and definite kind of thing, a potentiality for becoming at all, i.e. a bare potentiality.[3]
2. Proximate Matter: What Material Substances Are Made From
Prime matter together with substantial form are principles not only of the coming to be (generation) of substances, but also of the continued being of substances after they come to be. Together substantial form and prime matter constitute material things as substantial unities or wholes, singular substances (of given species or kind) which exist in themselves (per se) and not in another (per accidens). Thus, for Aristotle and Thomas Aquinas, substances have an intrinsic unity or oneness; substances are not composed of parts which are themselves actual substances. The potentiality to become other substances, i.e., prime matter, is actualized by a thing’s substantial form, but this substance itself came to be (or is sustained in being) from the matter provided by some prior substance(s) that were consumed (corrupted) in its generation (or nutrition). The substantial forms of those prior substances, however, set the range of possibilities for that matter to be actualized by another substantial form in some new substance. Not every material substance immediately has the potency to burn and produce ashes, for instance, but only wood or similar flammable substances.
Prime matter, in itself, is the potentiality to have any substantial form, although it never exists in reality without one; and yet the form it may have at any given time limits the new forms by which it may be actualized. Aquinas sometimes refers to the matter which has or is able to become a certain sort of substance as proximate matter because it is prime matter under a specific prior form which is close or proximate to what it will be, and being matter to these prior forms disposes it to the form which can and will actualize it. Being a component of one type of substance allows the prime matter, when that thing is corrupted, to become actualized in and as the specific sort of substance generated, and not as some other kind. For instance, water does not arise from just any lack (privation) of water, but from the lack of the form water in other material substances which dispose that matter to become and be water. Just as shapelessness in bronze (but not in tapioca pudding) is disposed to become a statue, so the prime matter in hydrogen and oxygen is disposed to become water (H2O) in the right combination, or to become hydrogen peroxide (H2O2) in a different combination, but not salt (NaCl). Being the matter of certain specific substances allows that (proximate) matter to become only certain other specific things. This entails that prime matter is not merely the lack of the new thing; prime matter is the lack of the form of a new thing and the potency to become the new thing in the old thing. Or more precisely, proximate matter is the potentiality to acquire certain forms according as prime matter is so disposed by being the matter for a prior (or subsequent) material substance of a certain type. The matter in an apple and as an apple is disposed to become matter for a human or a horse; it is proximate matter for these living substances, in way it was not so disposed when this matter was actualized by the form of the apple tree (as applewood), or by the forms of the dirt and water taken in by the tree as its nutrients.
Similarly, sodium (Na) and chlorine (Cl) are different substances with different properties and active powers and passive potencies, and they are each different from salt (NaCl), but they are proximate matter to becoming salt.
Sodium is a solid metallic element, one of the alkali metals; it has a crystalline form, is silver white in color, soft, malleable, ductile, opaque, electrically and thermally conductive, a little less dense than water, etc. … Chlorine is a gaseous non-metallic element, yellow-green in color, possessed of a disagreeable odor, is denser than air, non-conducting, etc. … Salt is a solid compound; it has cubic crystals, is breakable, non-conducting, white in color, opaque, possessed of a distinct flavor bearing its own name, etc.[4]
Sodium and chlorine have the potency to become salt among many other (but not any and every) potencies; for instance, they cannot immediately become water. Sodium and chlorine, then, are proximate matter to salt, but not to water. Although salt is in a sense “made from” sodium and chlorine, these are each distinct kinds of substances since we observe them to have distinct properties, active and passive potencies.
The set of physical properties that describes salt is different from that of sodium and from that of chlorine, and consequently we must say that neither sodium nor chlorine exists as such in salt. If either or both did so exist, their characteristic properties would be present.[5]
For Aristotle and Aquinas, it is a fundamental understanding of logic and experience that substances are what exist in their own right, in themselves or per se, and so they are unitary wholes. They do not and cannot have parts which are themselves substances. Remember from logic, primary substance is neither said of (predicated), nor exists in another (as an accident). but exists in itself: this dog, Fido; this man, Socrates; this horse, Flicka. Accidents exist in, and universals are predicated of, individual substances. If a whole were to be made up of diverse substances, such a whole would be an accidental arrangement of substances, either unorganized as heaps of stones, or as bricks, mortar, and timber is organized as a house, or metal and plastic – cogs and springs are organized as a machine, e.g., a watch or toy car. In all such cases, the accidental arrangement of substances – parts which exist per se – is an aggregate, an accidental whole, and as such does not exhibit any properties of a distinct or different sort from those found among the parts.
The hylomorphic understanding of material things of Aristotle and Aquinas, then, differs from scientific materialistic accounts of natural, physical things. In hylomorphism, prime matter and substantial form do compose substances, but these principles of change and of being are not themselves substances. Instead, they are physical principles that correspond to the potentiality and actuality of material substances which exist in and of themselves, i.e., in their own right.
Physicalist or materialist conceptions, however, claim that the composition of complex macroscopic objects out of prior proximate matter or simpler substances indicates that simpler substances actually exist in the complex. Thus, the composed or complex objects ‘just are,’ i.e., are reducible to, the arrangement of the prior or simpler ones, or are eliminable, in that the molecular/atomic/subatomic constituents completely explain the macroscopic objects and descriptions in terms of such constituents can replace the macroscopic/commonsense names. Such materialistic theories come in many varieties. Whereas hylomorphism acknowledges that material substances are made from prior (proximate) material substances, physicalism/scientific materialism, by contrast, claims material things are made out of prior (more fundamental) material substances. Ancient materialists like Democritus proposed a crude, somewhat simplistic, atomism wherein all that was really real were tiny, invisible atoms (uncut – a-temnein in Greek) of different kinds swirling in the void, As ancient atomists claimed commonsense objects were less real arrangements of atoms, so modern materialist/physicalist theories assert fundamentally equivalent claims:
According to [reductive materialism], the macroscopic properties of a physical object are reducible to the microstructure of, and interaction between, the object’s atomic and molecular parts. That is, reductive materialism claims to fully explain the macroscopic features of things in terms of their microstructures by asserting that the two sorts of properties are strictly identical. … [T]he macroscopic properties are explained by the microstructure in the sense that two are claimed to be really the same, with the microstructure providing the more precise and basic description. Thus, the macroscopic features are always and only features of the material constituents arranged in a particular manner because, ultimately, they just are properties of the material constituents.[6]
Whether the materialism is eliminative (scientific accounts replaces commonsense “folk” descriptions), reductive (scientific laws describing molecules and atoms explain the macroscopic objects, their properties, and behavior), emergent (observable properties emerge from the atomic level), or supervenient (the observable correlates with the microscopic without being strictly caused by them according to a generalizable law) or, in the case of biological or artificial organisms, functionalist (states of the appropriately organized physical systems (of various constituents)), all such theories assert that the macroscopic objects and properties result from microscopic physical constituents which exist in their own right (as substances) in the macroscopic. Such collections of micro-substance (rocks, trees, dogs, human beings, planets, stars) exist in a secondary and derivative sense, then, as an aggregate or collection of (coordinated) parts, but not as new independent, per se existing substances. Whatever seemingly new, observable properties or activities the aggregates exhibit result from the mechanical or mechanistic interaction of constituents at the micro-level.
[I]f mechanism is right, then every stuff is an aggregate of particles and none is a substance. If atoms are arrangements of particles, then they are aggregates; and if molecules are arrangements of atoms they too are aggregates. Nothing other than truly elementary particles would be substances.[7]
All these types of materialist accounts – reductive, eliminative, supervenience, emergent, functionalist – however, face difficulties in explaining observable objects in terms of being ‘nothing but’ more fundamental elements, and able to have properties and powers not possessed by the elements.
For example, when a tree is burned and turned to ash, what happens [according to atomism] is that the particles that were once arranged so as to form a tree are now rearranged so as to form ash. But a problem with this view is that it entails that dogs, trees, stones, and the like are not really substances. The true substances are the fundamental particles, and to be a dog, a tree, or a stone is just for these particles to take on a certain kind of accidental form. Yet this seems clearly wrong insofar as these and other natural objects appear to have causal powers that are irreducible to the sum of the causal powers of fundamental particles.[8]
If the micro-constituents only interact with each other according to the properties and powers present in them already, there is no way for new properties to arise according to what we already understand about such (mechanistic) interactions. For example, if chemical elements actually exist in a molecule, the latter would be an aggregate, an accidental arrangement of pre-existing elements (atoms) and their interaction would proceed according to the properties they have according to the elemental properties they already possess.
[I]t follows that the molecule could not have any new physical properties; it could have no properties that do not already belong to the parts of the aggregate…. But … an [accidental arrangement] does not cause already existing properties in a stuff to be destroyed, nor does it cause new kinds of properties to come to be….
[On the mechanistic model] a chemical reaction consists in each atom acting on the other by reason of an active property each already possesses, and each atom undergoing the action of the other by reason of a passive quality each already possesses. And just as linked parts of a machine do not change their sets of properties, neither would atoms. …
Reflecting on the theory, we see that the representation of atoms as aggregates does account for the union and separation of atoms, but that it does not explain the disappearance of some properties and the coming to be of others, except for adding the mass (mass-energy), which is conserved. (We might add that the total charge is conserved too.) So given that changes have occurred in almost all the properties, we know that something more than a mere [accidental] uniting must occur….[9]
The ‘something more’ than mere combination of existing substances (in the molecular, atomic, or subatomic constituents) is the generation of new substances with new properties and powers as determined by the new substantial form actualizing the potency of prime matter provided by the prior proximate matter from the prior substances. Since salt has properties and powers not present in either sodium or chlorine, one must conclude that a new substance has been generated from the prior ones, that the matter provided by the white metal and green gas has become actualized by a new substantial form, or better, that the potential for salt within the matter of sodium and chlorine has been made actual.
Not only do the wholes made from various constituent parts exhibit powers, activities, and properties distinct from those of their constituent parts, the (potential) parts themselves behave differently within wholes than they do when in isolation from them, either before being incorporated into the substantial whole, or after being separated out of it. Michael Dodds, OP, drawing on the work of William Wallace, OP, illustrates this point in the case of electrons both within a sodium atom and those external to (i.e., “free” of) any atom.
An electron in a sodium atom, for instance, may behave differently from a free electron because it now has new electromagnetic relationships, but it has those relationships precisely because it is no longer simply an electron: it has become a new substance with a new substantial form. It behaves as part of the sodium atom because it is now sodium (emphasis in the original).[10]
The difference in operation between such parts (electrons) when incorporated into a new substantial whole (sodium atom) versus when separated from such a whole is best explained by the parts existing as one substance (sodium) versus existing as another (a free electron). Dodds thus cites Wallace to elaborate:
A “free” electron (one not “bound” within an atom) is completely controlled by its own mass and electric charge. When within an atom, however, it “obeys” Bohr’s quantum rules–not falling into the nucleus or radiating when in its assigned orbit, making only its “allowed” transitions. On its own, each electron would be indifferent to the particular energy state it might occupy within the atom; within the atom, according to the Pauli exclusion principle, each electron is assigned to a unique state occupied by no other. The behavior of the electron in the Bohr atom of sodium is dictated not by the form of electron as this might exist outside the atom, but by the unifying form of sodium.[11]
This again indicates that substantial wholes are not mere accidental arrangements and aggregates of their constituent parts. That is, these differences between the properties or activities of wholes and their parts, as well as the differences between parts within wholes and as separate from them, indicates differences in being (substantial, and not merely accidental). As St. Thomas notes, each thing acts according to the kind of thing it is, and the kind of thing each is, is determined not by its matter, i.e., its constituents or proximate matter (much less by prime matter which all material things have in common), but by its substantial form:
From the diversity of forms, according to which the species of things are diversified, there also follows differences of operations. For, since each thing acts according as it is actual … and since every being is actual by its form, it is necessary that the operation of a thing follow its form. Therefore, if there are diverse forms, they must have diverse operations.[12]
Different substances, both the substantial wholes made from proximate matter and the proximate material parts existing separately apart as their own substance, each behave differently. And as things exhibit a difference in behavior, this observed fact indicates they are substantially different in being, different in kind or species (not mere accidental arrangements of aggregate parts).
Since a thing’s being is the source of its action, we can account for the action of the thing only if we account for its being. In particular, we can account for the action of the whole only if we account for the being of the whole. … If the “whole” is merely a conglomeration of parts, then it will always be the action of the part that accounts for the whole and not vice versa. … And if the action of the part, within the whole, is different from its action in isolation, we have reason to suspect that the being of the part within the whole is different from its being in isolation. … The substantial form is … the source of the characteristic activity of the substance. Making the substance to be what it is, it also causes the substance to act as it does.[13]
When material parts (as proximate matter) are incorporated into substantial wholes, they become unified through their prime matter being informed by a new substantial form. The substantial forms that matter had as pre-incorporated substances simply ceases to exist, though, as we will see, something of the constituent parts remain in the substance into which they are incorporated. The fact that what results from the coming together of certain elements or molecules (or subatomic particles, for that matter) exhibits powers, properties, and behaviors not found in the elements, etc, is objective evidence that there is a new substantial form informing the proximate matter. The ability to identify new powers and properties that go above and beyond those of constituent, proximate matter, establishes the objective conditions for identifying the generation (and corruption) of new substances out of prior ones, especially when and how new living substances come to be from non-living material elements (and vice versa).
Yet, even modern science demonstrates (while operating with physicalist/materialist assumptions), not only complex molecules, but even elements, or the subatomic particles from which they are made (see below), can change into each other, and, in principle, everything can eventually change into anything. Thus, throughout all kinds of substantial changes, something underlies the matter proximate to these apparent changes; that something is prime matter. The elements themselves, then, have both prime matter and substantial form. The prime matter is the principle that makes these things to be material and allows them to change, but it is not the elements themselves. The material substances are not reductively the result of the combination of elements, but the combination of elements in material substances is the result of the substantial form that prime matter has acquired. Water may be described as H2O because this liquid resulted from the gases hydrogen and oxygen, because it still has some of the powers and qualities of the elements, e.g. mass, and because the gases may be extracted for the liquid (through electrolysis). Nevertheless, the elements of hydrogen and oxygen are present only potentially and virtually (see below) in water. However, water is a single substance, and the substance of water has the form of water in prime matter, the elements of hydrogen and oxygen being the proximate matter to water, and potential to its substantial actuality.
It seems clear, as it was to Aristotle and Aquinas, however, that the proximate matter (material constituents) that more complex substances either arise from, or are corrupted into, is itself identifiable as separate from and, in a sense, more basic than the more complex ones to which they give rise. For instance, one can see that animals are composed of moist flesh and dry (drier) bone, blood of iron (for a bloody lip tastes metallic), sweat and tears of water and salt; in general, material objects of ordinary experience can be broken down into simpler parts identifiable as substances of given sorts. These parts appear to be composed of material things that definitely are substances when they are not being parts of animals; e.g. bone looks like white stone, and both Aristotle and Aquinas thought it was composed of earth, which for them is one of the four basic elements. Today, we would say that material composition of bone consists mostly of calcium. The hylomorphism of Aristotle and Aquinas, however, maintains that new substances arise from the potency of (proximate) matter through the combining of elements (or ‘blending’ as Aristotle says (see below)) precisely because new features and capacities are present in the resultant combination that were not present in prior components. This combination, however, goes beyond mere aggregation of substantially independent constituent parts. More complex substances are ‘made from’ prior simpler substance insofar as the matter of the prior substances takes on the new resultant substantial form, but they are not ‘made out of’ the prior substances as though these constituents still existed per se, as actual substances.
3. Virtual Presence: Chemical elements in complex substances
Aristotle and Aquinas, recognize that although the prior substances, i.e. the elements and molecular compounds, from which a given substance is formed, are the proximate matter of that substance, and that these components have thus become that substance into which they were incorporated, the components in some sense remain in them, yet nevertheless do not have the full actuality of being substances in their own right.
In On Generation and Corruption, Aristotle considers the difficulties raised by saying that material constituents ‘combine’ to form another substance distinct from them. … It appears contradictory to say that the parts of substances are actually substances, on the one hand, and just plain false to say the parts of substances are not combined in a substance, on the other. Anything one calls a substance cannot have other actual substances as parts, for then two substances would be in the same place at the same time, and the same thing would be two things, in the same respect, i.e., as an actual substance. Thus, a certain piece of matter, say a bone, would be actually and substantially both an animal and earth (a non-animal) at the same time; but it also seems wrong to say that bones are not made of earth.[14]
Both Aristotle and Aquinas believe for such parts to have the same substantial unity when they are parts of other things as they do when they are not parts would entail that the what these parts come together to compose are not substances. If, for instance, the bones of an animal are actually earth or calcium, then the animal would not be itself a single substance characterized by an intrinsic unity, but an accidental unity, analogous to an arrangement of bricks that form a house, or pieces of metal fitted together to make a machine.
Aristotle’s solution is to propose a theory of the continued presence of the constituents by means of their powers. Instead of allowing that the parts to exist in the combined substance with the full actuality of substances, Aristotle says that these other substances, i.e., the elements, in a sense are and in a sense are not in the combined substance; they exist potentially [but not actually] in the substances into which they changed.[15]
Aristotle’s point is that the elements that combine to form blended or mixed bodies, not only have the potency of matter from which they came, but by being proximate matter for the new substance, they give to the resultant compound certain active and passive qualities or powers by which they can be identified as parts of the compound.
Since, however, some things are-potentially while others are-actually, the constituents combined in a compound can ‘be’ in a sense and yet ‘not-be.’ The compound may be-actually other than the constituents from which it has resulted; nevertheless, each of them may be-potentially what it was before they were combined, and both of them may survive undestroyed. . .. The constituents, therefore, neither persist actually, as ‘body’ and ‘white’ persist: nor are they destroyed (either one of them or both), for their ‘power of action’ is preserved.[16]
The ‘power of action’ preserved in the compound, however, is a power of the compound as a new, unitary substance, though obviously the power belongs to it in virtue of proximate matter of which it is composed.
Since ‘matter’ is the principle of potency, the matter of the elements becomes the matter of the substance they compose, but the elements are present potentially in the newly composed substance. So, while there is only one substance that results from the composition of various elements, the new substance has the powers of the elements which came together in its composition. Aquinas elaborates Aristotle’s theory, saying that the elements are not actually in the substance, but they are there virtually, i.e., by their power (virtus).[17]
While the new substance has its own substantial form, distinct from that of the proximate matter, certain qualities of the matter from which it was generated remain in the resultant substance. As Aquinas explains
Therefore, we must say, in accordance with the Philosopher in Book I of On Generation [and Corruption], that forms of the elements remain in the mixed body, not in act (actu), but by their power (virtute). For the proper qualities of the elements remain, though diminished (remisse); and in these qualities is the power of the forms of the elements. And such quality of the mixture is the proper disposition for the substantial form of the mixed body; for instance, the form of a stone, or of any sort of soul.[18]
While it is common to call such presence ‘virtual,’ Christopher Decaen notes how inadequate this term is for what Aquinas designates as virtute. “In modern English the word ‘virtually’ means ‘more or less,’ or ‘practically,’ or ‘pretty much but not quite.’ … which is hardly a philosophically precise manner of speaking.”[19] Much better, he urges, to say that elements remain in mixed bodies ‘by their power.’ Decaen summarizes Aquinas’s position:
Thus, Thomas’s answer to the question of how the elements exist in a mixed substance is that they exist by their powers existing, and this means that their substantial forms in and of themselves do not exist in actuality, and in fact neither do their active and passive qualities, at least not to their full “excellence.” Speaking most properly, both are preserved only in potentia, although … the preservation of the elemental powers is both more evident and less potential than that of the elemental substantial forms.[20]
The elements of the mixed body, then, are not actually in the new substance as actual substances in their own right, nor with their substantial form actualizing matter. Yet certain of their properties or proper accidents, some powers to act or be acted upon, remain and become the accidents and powers of the new substance composed of these elements.
Thus, while a substance may act in virtue of the material elements which compose it, it is the substance which acts and not the elements; nor do elements have their own distinct activities.[21]
Again, every substance is a unitary whole and cannot have other actual substances as its parts. In the reductionism common to various versions of physicalism, macroscopic objects are reducible to (i.e., being ‘nothing but’) collection of substances (atoms or subatomic particles) being unified in a secondary and incidental way, i.e., as an accidental whole. By contrast, for Aristotle and Aquinas, individual ‘mixed bodies,’ those macroscopic objects, while having been composed from the proximate matter (ultimately) of atoms or subatomic particles, act as a whole and in ways that go above and beyond the substances so mixed. Each macroscopic ‘mixed’ body, thus, is a unitary substance with the constituents having been changed in their being into the new substantial whole, and its parts exist in the new substance in a secondary way as potential and virtual. On hylomorphism, substances are irreducible to their chemical (molecular and atomic) make-up, yet their chemicals that were changed into the new substances nevertheless condition and in a certain sense (materially) explain some of the behavior and activities of the substances into which they have been incorporated, while the new substances exhibit genuinely new and different activities not accounted for by their chemical make-up alone.
4. What Underlies the Conversion between Particles and Energy
Despite the irreducibility of substances to chemical parts, modern atomic and particle physics nevertheless show that the ultimate matter of the proximate and potential constituents of everything can ultimately and theoretically be converted into other ultimate constituents. Prime matter, however, must serve as an ultimate substrate of such ultimate transformations.
According to current physical theory, even quarks can be substantially transformed into other quarks: for example, a quark of one flavour can transform into a quark of another flavour through the weak interaction. In beta decay, where a neutron decays into a proton, an electron, and an electron antineutrino, one of the down quarks in the neutron decays into an up quark by emitting a W*– boson. Such transformations are held to be consistent with the conservation laws, and according to quantum theory quark transformation must eventually occur. … The point here is that the current ‘rock bottom’ level for physics, as for all previous putative lowest levels, involves (and must involve) substantial transformations. Such changes occur at all levels of physical reality, and prime matter is necessary for their possibility.[22]
The ultimate material constituents, moreover, can be converted into energy, and energy can similarly be converted into matter. Werner Heisenberg, the pioneering physicist of quantum theory, sees in this universal mutability of the physical, even down to the most basic and elemental levels, resonances with hylomorphism:
If we compare this situation with the Aristotelian concepts of matter and form, we can say that the matter of Aristotle, which is mere ‘potentia’, should be compared to our concept of energy, which gets into ‘actuality’ by means of the form, when the elementary particle is created.
All the elementary particles can, at sufficiently high energies, be transmuted into other particles, or they can be created from kinetic energy and can be annihilated into energy, for instance into radiation. Therefore, we have here actually the final proof for the unity of matter. All elementary particles are made of the same substance, which we may call energy or universal matter; they are just forms in which matter can appear.[23]
Nevertheless, there still seems to be some principle that underlies each of these two ways of being physical, but this substratum cannot exist without being in actuality one or the other, matter or some observable form of energy. As underlying the transformation between particles (or strings or fields or whatever), Heisenberg identifies this substrate as ‘energy or universal matter.’ Oderberg notes, however, that energy, as actually described and discussed in physical theory, itself takes various forms and is actualized in varying manners.
We now have identified gravitational energy, kinetic energy, heat energy, elastic energy, electrical energy, chemical energy, radiant energy, nuclear energy, and mass energy, among others. As Feynman says, each of these has its own equations yet each is but a manifestation of ‘energy going in and out’, always conserved in total.[24]
He thus suggests that what underlies all such fundamental changes – conversions between the various kinds of energy, as well as substantial transformations between particles and the conversion of mass to energy and energy to mass – cannot be any determinate form of matter or particle, but some indeterminate, pure potentiality; an energy more basic than the observable forms: kinetic, electro-magnetic, etc. Oderberg suggests, therefore, that
all of the elementary particles can be transformed into other particles. … [A]s long as some transformations can occur at the elementary level, we know that energy functions as the underlying substratum.[25]
Whereas Dodds notes
that Heisenberg has not yet achieved a level as basic as Aristotle since energy itself already has some actuality and so is not the same principle as Aristotle’s primary matter which, having no actuality at all, is more basic than energy.[26]
Oderberg’s underlying energy (and perhaps Heisenberg’s as well) is just this basic principle of potentiality lacking any actuality, yet which must exist as a principle of continuity between particle and/or energy transformations. Even with the advances of modern particle physics, there is still a theoretical need, it seems, for the notion of prime matter – call it universal matter, undifferentiated energy, mass/energy substrate – the pure potentiality of substances of given kinds (mass) to change into others or into energy of different sorts (heat, radiation, nuclear, chemical, etc.).
5. Principle of Corruptibility
Because prime matter serves as a principle of continuity between changes of one substance into another, it is also the principle of corruptibility within material things. While prime matter whenever and wherever it exists is always actualized by a thing’s substantial form, no substantial form completely actualizes the infinite potentiality of prime matter. As Aquinas explains in On the Principles of Nature, chapter 2. 2, “matter is never without some privation, for insofar as [while] it is under one form it has the privation of another, and conversely.” Every material thing, therefore, retains the potential in prime matter to become other than it is, i.e., for a new substance to be generated out of its matter, and for its matter to serve as the proximate matter to a new material substance.
Primary matter is the principle of corruption. Since primary matter is pure potency, it has a radical capacity for all forms. The form which actualizes or determines it at any given moment does not completely exhaust this capacity. In possessing any particular form, primary matter always has the privation of other forms. Primary matter therefore explains the contingency and corruptibility of material things.[27]
Every generation of something new, then, necessarily entails the corruption of something prior. Corruptibility, then, is inherent in material things simply in virtue of their being material.[28]
Incidentally, Aquinas appeals to the inherent corruptibility of material things when explaining how natural evils (such as disease, death, and decay) can be compatible with God, who is all good. He notes that insofar as generation and continuation in being constitutes the good of a particular material thing (see Chapter 5 of this Overview on Metaphysics), so the corruption and loss of a thing’s substantial form in such generations are natural evils for these prior substances. Aquinas thus acknowledges that such natural evils are inherent in the universal natural, material order, yet they contribute to a higher-order, universal good which God brings out of such evils and so are a necessary part of the good of the material world (among other natural and moral goods).
Corruption and defects in natural things are said to be contrary to some particular nature, but nevertheless they belong to the plan (intentione) of universal nature; insofar as the defect in one thing yields to the good of another, or even to the [good] of the whole universe. For the corruption of one thing is the generation of another, and through this a species is kept in existence.[29]
Corruption, from the perspective of an individual material thing constitutes its destruction, and so is for it an evil; yet this evil is necessary for the generation of others of the same or different species, which are goods. Moreover, the cycle, pattern, and order of the whole of nature is a higher good for which corruption is necessary. Such corruption is made possible by matter’s insatiable capacity, its potentiality always to take on other substantial forms than the ones by which it is currently made actual.
6. Principle of Individuation
In addition to being the principle of continuity for substantial changes and so the principle of corruptibility, primary matter is also the principle of individuation, the inherent, physical reason why a single species has many individual members. The members, despite sharing in one substantial form (dog, for instance), are each distinct from each other and so are each distinct material individuals (Rover, Spot, or Lassie). They each ‘occupy,’ as it were, separate and distinct parcels of matter, distinguished, first, by different locations in space and separate physical dimensions. Something inherent in these substances individuates each from the others, and differentiates them as particular members of the universal species. There must be, then, a principle which makes each individual to be an individual.
The substantial form cannot be the principle of individuation since it is specifically the same in all individuals of the species. All individuals of the species have the same specific substantial form. All dogs, for instance, have the form of dog. The form “dog” makes a dog to be a dog but does not account for the distinction between two dogs. There must be a substantial principle that makes Spot to be Spot and Rover to be Rover. But there are only two substantial principles, primary matter and substantial form. If the principle of individuation is not associated with substantial form, it must be associated with primary matter.[30]
Aquinas locates the principle of individuation in prime matter. Prime matter, just as such, has pure potentiality and has no actuality, no determination of its own. The principle of individuation, then, must be prime matter when considered in relation to the accident of quantity, what he calls “quantified signate matter” or “matter designated by quantity” (materia signata quantitate).
If it is asked how this form differs from that, there will be no other reason than that it is in other signate matter. Nor is there found another reason why this matter is divided from that except because of its quantity. And so, matter subject to dimension is understood to be the principle of this diversity.[31]
Matter, insofar as it has designated dimensions, is the principle of the individuation of form. And for this reason a singular thing is numerically one and divided from other things as a result of matter.[32]
And so dimensive quantity itself is a certain principle of individuation in forms of this kind, namely, inasmuch as numerically distinct forms are in different parts of the matter.[33]
Prime matter, whenever and wherever it exists, exists as a substance of a given sort, as informed by a specific substantial form. In itself, prime matter has no actuality, but is only actual through substantial form. To identify which ‘part’ of matter is so informed and to locate it ‘here’ as distinct from ‘there,’ it has to have at least the actuality of quantity, which quantity is (or was) an attribute of the proximate matter the substance was made from.
The principle of individuation is primary matter considered in relation to the accident of quantity. Primary matter, considered in itself, is pure potency, with no actuality to distinguish “this” primary matter from “that”. The primary matter of this substance, considered together with the accident of quantity, is distinguishable from the primary matter of “that” substance. “Quantity” implies extension, which implies parts distinguishable in terms of place. Primary matter in association with the accident of quantity accounts for the multiplication of a species in many individuals.[34]
This dog, Fido, is a distinct dog from that one, Spot, because it was generated from distinct matter provided by (possibly) distinct parents, located in physically distinct locations, and has consumed a distinct (perhaps greater) quantity of food, etc.
So it is prime matter qua something requiring dimension in order for it to take on form at all — again, prime matter as designated or marked-off as being here rather than there — that individuates one material substance from another.[35]
Such differentiations depend on matter having at least the attribute of quantity, though such quantities (mass, position in space) may be possessed successively by the various substances which provided the proximate matter to each substance over the duration of its existence (life).
[1] On the Principles of Nature, c. 2.7.
[2] Ibid., c. 2.9.
[3] Frederick Coppleston, SJ, A History of Philosophy, Volume I: Greece and Rome, (NY: Doubleday, 1985), 307-308.
[4] Richard Connell, Substance and Modern Science (Center for Thomistic Studies, 1988), p.82.
[5] Ibid., p. 83.
[6] Magee, op. cit., p. 4-5.
[7] Connell, op cit. p. 81.
[8] Feser, Aristotle’s Revenge, p. 30.
[9] Connell, op. cit., pp. 83, 86.
[10] Dodds, op. cit., p. 58
[11] William Wallace, The Modeling of Nature: Philosophy of Science and Philosophy of Nature in Synthesis. (Washington, DC: The Catholic University of America Press, 1996) pp. 46-7; 57 as cited by Dodds, ibid.
[12] SCG 3, 97, no. 4.
[13] Michael J. Dodds, OP, “Top Down, Bottom Up or Inside Out? Retrieving Aristotelian Causality in Contemporary Science,” Jacques Maritain Center at the University of Notre Dame, Indiana, Thomistic Institute, July 25, 1997, pp. 7-8, 11.
[14] Magee, op. cit., p. 95.
[15] Ibid.
[16] On Generation and Corruption 1.10 (327b23-26,29-31).
[17] Magee, op. cit.
[18] ST Ia q. 76, a. 4, ad 4.
[19] Christopher Decaen, “Elemental Virtual Presence in St. Thomas,” The Thomist 64 (2000), pp. 275-6.
[20] Ibid., p. 293.
[21] Magee, op. cit., p. 96.
[22] David S. Oderberg, “Is Prime Matter Energy?” Australasian Journal of Philosophy, 101:3 (2023), 537.
[23] Werner Heisenberg, Physics and Philosophy (New York: Harper and Brothers, 1959) p. 160, as quoted by Dodds, Philosophy of Nature, p. 11.
[24] Oderberg, art. cit., p. 539.
[25] Ibid., p. 540.
[26] Dodds, “Top Down,” p. 19, n. 46.
[27] Dodds, Philosophy of Nature, p. 38.
[28] Aristotle and Aquinas in fact believed that such corruptibility was inherent only in the four elements (earth, air, fire, and water) that they believed constituted the ultimate identifiable matter of the terrestrial world. This world, made of these four elements, on the Ptolemaic (also called ‘geocentric’) model of the cosmos, sits at the center of the universe below or within the heavens, concentric crystalline spheres (one for each known ‘planet’: the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn (a ‘planet’ being a light that ‘wandered’ against the outermost sphere of the fixed stars which maintain their relation and relative position to each other)). The terrestrial world is thus also called the sublunary world, essentially different from the celestial realm of the spheres. And while the sublunary world is composed of four corruptible elements, the celestial is composed of a fifth, incorruptible element, the quintessence. Unfortunately (or fortunately), the field of observational astronomy which Galileo initiated through his invention of the telescope rendered the ancient cosmography which Aquinas inherited from Ptolemy and Aristotle untenable. Aristotle’s cosmology, however, grounded as it is in hylomorphism and the observation of substantial change, remains unaffected by the falsification of the geocentric model.
[29] ST Ia, q. 22, a. 2 Reply Obj. 2.
[30] Dodds, Philosophy of Nature, p, 40.
[31] Commentary on Boethius’ On the Trinity, q. 4, a. 2, ad 4.
[32] Commentary on Aristotle’s Metaphysics, Book V, lect. 8, no. 876.
[33] ST IIIa, q. 77, a. 2.
[34] Dodds, Philosophy of Nature, p, 40.
[35] Edward Feser. Scholastic Metaphysics: A Contemporary Introduction (Editiones Scholasticae 2014), Kindle Edition, p. 256.
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