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by Dr. R. Glen Coughlin
Thomas Aquinas College
St. Thomas Day Lecture
March 8, 2021


The topic I wish to address concerns the proper order of learning, in particular, the order between natural philosophy and metaphysics. My question is: should we study metaphysics or natural philosophy first? I will argue for the traditional view that we need to study natural philosophy first because otherwise we do not have a subject to study. This traditional view is controverted by many modern Thomists who think we can begin with the basic notion of being that everyone has from experience or with something a little more refined, but not dependent on natural philosophy. I will try to show that all the alternative positions share a certain fundamental mistake. Recognizing this fact will go far to helping us see the need for proofs in natural philosophy.


Part One – Two Preliminaries

To start, we need to discuss two preliminaries: first, that science is an assimilation to reality and, secondly, that sciences are divided by their modes of definition. The first part of this lecture will lay these preliminaries out, not at great length but, I hope, sufficiently. In the second part I will argue that the conditions of the science of metaphysics can be met only if we prove in natural philosophy that there are immaterial beings.


First Preliminary – Science is about the Real

What, then, is science? First and foremost it is a sort of knowledge and so assimilation of the mind to reality. When I know what a triangle is, in some way my mind must be assimilated to the nature triangle. And triangle must be in me in some way, for the activity of knowing it is in my mind. I “have it in mind.” In the de Anima, Aristotle notes that Empedocles thought the soul was made out of the four elements because like is known by like. He thought that, if we know a horse, we must have in us something of the horse, and he hit upon the elements as that something. His position, as Aristotle shows, cannot be right because it implies that we have things in our minds in just the way they are in reality, so that if I know what a horse is, I have a little horse in my head. But he is right that the thing known must be somehow reproduced in our minds and senses. If we in fact know things, we know them by having them in our minds or senses. Although I cannot have an actual horse in my head when I know a horse, I have to have something like a horse in my mind if I really do know the horse and the knowing really is in my mind. Since thinking and sensing are acts which take place within us, the objects of our thoughts and sensations must be in our minds and sense powers in some way. So our knowing powers are brought into activity by being made like to the things they know. That is what I am calling “assimilation,” namely, the likening or conforming of our knowing powers to their objects.

To what do we become assimilated when we know? If we know, we know something true, that is, our minds reflect what is real. Truth, says St. Thomas, is the correspondence between the mind and reality. Consequently, science is the grasp of some real thing, not of a nothing or of a fiction or a fantasy. We don’t have science about things that are not real in any way. But now we already need to clarify, because things can be real in different ways and not all those ways are required for knowledge.

We might think that if knowledge is of what is real, dodo birds and dinosaurs cannot be objects of knowledge, and though there may be many reasons that we fail to have knowledge of these, we do not fail to have knowledge of them by mere dint of their happening not to exist right now in the physical world. Were all squares to be somehow wiped out, geometrical knowledge would be unchanged. Even as things are, we have no way of knowing that there actually are perfect squares in nature, outside the mind. How could we ever be sure of this? We would have to measure angles and lengths, but every measurement is subject to inevitable imprecisions, however small they may be. Nevertheless, this fact does not shake our confidence that there is such a thing as a science of squares. So, too, we can have knowledge of an extinct species. The dodo bird has gone the way of the dodo, but we can still (supposing we can dredge up enough DNA and other evidence) have knowledge about dodo birds. So, even though knowledge must be of what is real, it does not have to be of what exists in the real world right now or even of what did or will exist at any particular time in the real world.

On the other hand, if the object of knowledge need not be a thing in the natural world, still less can it be a mere fiction. We can have a poetics dealing with fiction, but that’s because fiction is a certain kind of artefact that has certain real principles. We do not have science about the particular fictions we make up, about hobbits, for example. Whether we invent the fiction deliberately, for entertainment’s sake, or unwittingly, by committing an error, makes no difference. There is no science of phlogiston any more than there is one of hobbits, however much some thinkers may have believed that this hypothetical substance really existed. They did not have science; they had its polar opposite, error.

We can be deceived into thinking we have knowledge in such cases in at least two ways. We may simply think we have proof or experience that the thing in question exists (and so is possible) even when we, in fact, do not. For example, we might really believe we have seen a ghost. A more interesting case is this: we may think that because we can make true “if – then” statements about a thing, we have a sort of knowledge of it. We might think we have said something true when we say that “if angels exist, they have intellects.” In fact, we have said something true, but not, properly speaking, about angels. We have said something true about the relation between the antecedent (“if angels exist”) and the consequent (“they have intellects”). To use St. Thomas’ example, “If men are asses, men are irrational.” This is a true statement despite the fact that both the antecedent and the consequent are not only false but absurd. The truth of such statements is not about anything in the world; it is not about men or asses. It is only about the relation between the antecedent and the consequent, about a being of reason, namely, the logical connection between the parts of the sentence. We could easily form as many such sentences as we please: “if wishes were horses, beggars would ride;” “if the moon is made of cheese, it is edible.” No one would think we have discovered an easy and royal road to science.

When we study something which is a self-contradiction, whether the greatest prime number or phlogiston (supposing that phlogiston is in fact absurd and not just a possible though unreal thing), that’s the best we can do, namely, recognize what would be true if something absurd could be true. I might say, e.g., “if there is a greatest prime number, it is odd.” Such sentences do not express an assimilation to anything real except the connection between the antecedent and the consequent. If, on the other hand, we know that the antecedent is true and that its subject real, we are in a different situation: for then we know that there is a thing to which we are assimilated and about which the consequence is true. If an angel appeared to me in such a way that I somehow knew it was not a physical but an immaterial thing, I could prove, using an argument that St. Thomas provides, that it was intellectual (because it is immaterial) and I would thereby be assimilated to a real being and have a piece of real knowledge about it.

So science is about a thing the reality of which is not quite up to the solid reality of the physical world and not quite so unreal as the unreality of the merely imagined or invented. What is this middle sense of “real”? Perhaps the best clue is a fact already noted: we have knowledge of geometry even if we do not know that the objects of geometry exist in the real world. How are the objects of geometry more real than mere fictions or errors? They are really possible natures, even if they do not currently exist anywhere, even if they have never existed and never will exist. In geometry we prove, from the things we grant as possible from the beginning, that our objects are really possible, e.g., we construct a dodecahedron using principles which are either self-evident or are consequences of self-evident facts. The same can be said about an extinct species: we can understand something about them by starting from their effects and remains, which we know are really possible things, i.e., things that have no inherent contradictions, precisely because they are in our experience. Since we know that these effects are real, we know they are possible, and since we know they are possible, we know that their causes are possible; in fact, since the effects are real, we know their cause are or at least were real in the even stronger sense that they existed at some particular time.

So, because science is an assimilation to reality, I cannot have science of an absurdity, whether I recognize it to be such or not, for there would be nothing to be assimilated to, a self-contradiction being about as non-existent as anything can get. To push on a little further: Neither can I have science of what is possible but not known to be such. In this case, my mind is not linked to reality except according to belief or prejudice or a mere guess. Until I prove, for example, that the dodecahedron is a real possibility, rather than something about which I simply do not see the impossibility, I do not have science about it, but at best true opinion.

It remains that to have a science we have to know that we have a subject which is an intrinsically possible nature. Bur how do we know this about any proposed subject? It is most important to note that we certainly cannot conclude from our not seeing a contradiction that there is no contradiction in a proposed subject. The neophyte arithmetician might think there can be a seventeen-sided regular solid or a greatest prime number, but his failure to see the latent contradiction in these concepts is no basis for saying there is no contradiction or, worse, that seventeen-sided regular solids and greatest prime numbers are really possible and so are fine subjects for scientific study. In practical affairs, where events may press us to make judgements without having all the facts at our disposal, we may sometimes be forced to say, “I see no reason not to take this or that line of action,” but to argue thus in speculative matters cannot constitute science, however often we may fall into this mode of thought. In fact, we very often hear someone say, “I don’t see why this or that can’t be”, as if that is a reason to say the thing is. Unfortunately, ignorance is not bliss and not seeing a contradiction is not the same as seeing that there is no contradiction.

So what is the ground for saying there really is a subject to be investigated in any particular case? How can we be assured that any particular proposal is actually possible?

Two possible paths are open. First, we can simply have direct experience of the subject. For example, we know that dogs are possible because we have seen them. Secondly, we can start from what we see and so know to be possible and argue to other objects which are necessarily connected with them, as properties, principles, causes, or effects. For example, from the observed (and so really possible) red-shift of stars we conclude to its cause, the expansion of the universe. Likewise, Euclid knows that a circle can be drawn because he can do it (perhaps only in his imagination, but that is enough), and, using this and other principles which are self-evident, eventually argues that there is, in fact, such a thing as a dodecahedron. Without either being directly faced with the reality of a thing or else proving that a thing must be real given something else with which we are directly faced, we cannot know that the “things” we hope to study are anything more than chimeras. Otherwise we risk giving to “airy nothing a local habitation and a name,” a task more appropriate for the poet than for the philosopher.

In essence, what I have been arguing is that science cannot be based on a mere quid nominis, or definition of a name. I can certainly impose a name on any series of words, including those which involve self-contradiction – I can insist that “blitrig” means “square-circle.” Such a merely nominal definition cannot of itself be the basis of science. For if the nominal definition should express something self-contradictory, there will be no science of that subject. And unless I know that the thing named exists either by experience or by some inference from experience, I do not know that my quid nominis does not harbor a latent contradiction. The mere fact that I have not seen that it does harbor such a contradiction is not a ground sufficient for the scientist to say that it does not.

For this reason, the question an est precedes the question quid est in science. As St. Thomas says,

For because there is no quiddity or essence of a non-being, no one is able to know the “what it is” about what does not exist; but one is able to know the signification of the name, or the notion composed from many names: just as one is able to know what this name “goat-stag” … signifies, because it signifies a certain animal composed from a goat and a stag: but it is impossible to know the “what it is” of a goat-stag, because there is no such thing in rerum natura.

This is why Aristotle argues that to have science we must know both that the subject exists and what it is, and that knowing that it is comes first, and why St. Thomas says, “It is vain to seek what a thing is if one does not know that it is.” It is true that the signification of the name is needed – without it we would not even know what we are talking about or whether we have found it to exist – but only when that existence is established are we sure that there really is something there to be understood, that we are not just off on a wild goose chase. So the first preliminary is that science is about things which are real in the sense I have been discussing and which are known to be such.


Second Preliminary – Modes of Definition

The second preliminary we have to consider is how to define the sciences, or, more proximately, how to define metaphysics. Since metaphysics is a science, and generally the genus is a good starting place for finding a definition, we might ask what a science is.

First, science in the Aristotelian sense amounts to a knowledge embodied in a syllogism or a series of syllogisms, the first premises of which are self-evident principles. A syllogism has a middle term and, in science, the middle term is the definition of the subject. We proceed to a scientific understanding of mobile being, for example, from the definition of what is formal in the notion of mobile being, namely, motion or change; we have the science of triangles based on the definition of a triangle. That definition becomes the middle term in our syllogism, that is, we use it to show that some property belongs to the subject as such.

In distinguishing sciences from each other, St. Thomas argues that sciences should be divided by the sorts of definitions we have of the subjects. He argues that, because science is a kind of knowledge, it should be divided by degrees of “knowability” or “intelligibility.” This amounts to saying that sciences should be divided by the sort of definition we can give of the subject, for the intelligibility of the subject is reflected in the sort of definition we can give.

But how can some definitions be more intelligible than others? Here we are not concerned with a definition being less intelligible because it is wrong or imperfect, but with definitions which, even though they are as perfect as they can be, are more or less intelligible than other such perfect definitions. The definition of triangle, “a three-sided plane figure” is intrinsically more intelligible than the definition of motion, “the act of the potential as such” even if both are as good a definition of their respective subjects as you are going to find. The difference here is in the sorts of things you are trying to define – an abstract mathematical being or a concrete physical becoming. The one is removed from matter and motion, the other is mired in matter and is motion. We should consider here a little more at the different ways that matter and motion can be involved in the definition of a thing, since these will determine the intelligibility of those definitions.

First, because the human mind is immaterial, its object must be in some way immaterial. When I know what “man” is, I know this universally, that is, without the individuating principle of matter. To know man, I must know that man is a material thing, that he is made of flesh and bone, but I do not and even cannot know with my mind the individual flesh and bones that constitute Socrates. The drawing out or abstraction of the universal nature of man from individual men keeps a sort of common matter, flesh and bones in general, though it leaves aside the matter that makes a man this particular individual, that is, it leaves aside this flesh and bone. But this removal from matter is due to the nature of my mind, not to the nature of man. Man as it exists outside my mind is always individual; in my mind, always universal. Since the human mind receives even material things in this immaterial way, it must itself be immaterial – the immateriality must be due to the mind and not to the object – and so, from the point of view of the power of the mind, things are intelligible to the extent that they are removed from matter.

Secondly, we can look at the subject which we know by the particular kind of knowing called “science.” Aristotle argues that we only have science of necessary things, and St. Thomas follows suit. If a thing could be otherwise, my claims about it could become false without their having changed at all. If Socrates is seated and I think he is seated, I am right, but if I continue to think he is when he gets up, I become wrong even though I have not changed my mind – in fact, not changing my mind is the problem. So if science is to be a stable knowledge, it will have to be about things that are not able to be otherwise or, in other words, about things that are necessary. But what is in motion is to that extent not necessary but changeable, and therefore not a fit subject of science.

Since, then, things are objects of speculative science insofar as they are without matter and motion, and the divisions of the sciences should not be made on just any basis but on the basis of what belongs to the sciences as such, St. Thomas concludes that “speculative sciences are distinguished according to the order of remotion from matter and motion.”

It will be useful to think a little more about this “remotion from matter” and how it is found in the different sciences. “Remotio” might be translated “removal,” so the sense is that when we think of an object, we think of it without the matter that is somehow conjoined with that object in reality. This is, properly speaking, what abstraction from matter means. In the case of the natural sciences, we think of things like man or electron and we treat them universally, not as individuals. There is no science of Socrates or of this particular electron, there is only a science of man or of electron in general. But in order to think of man in general, we do have to think of flesh and bones, that is, of a kind of matter. So we abstract only from the particular material, this flesh and these bones, in which the natures we are concerned with actually exist, not from flesh and bones in general. The material from which we abstract in natural science is called individual sensible matter – “individual,” because it belongs to this one man, e.g., and not to man in general; “sensible,” because we are aware of it through its sensible properties like hardness or color. And yet, in natural science, we must retain what is referred to as “common sensible matter,” matter such as flesh and bone rather than this flesh and this bone. We cannot think of man except as composed of flesh and bone, so our general consideration of man must still look to a sort of matter; St. Thomas calls this matter, “common matter.”

The things we deal with in mathematics are likewise abstracted or removed from matter, but now in a different way. First, we remove from our consideration sensible qualities. We are not concerned as to whether our triangles are hard or soft, bronze or plastic. By removing from our consideration sensible qualities, we also remove from consideration sensible matter, since sensible matter is matter as subject to sensible qualities. Unlike natural science, mathematics has no concern with the world of sensation. We proceed incorrectly if we think we need to judge our mathematics by how it lines up with the sensible world. In this, mathematics and natural philosophy differ. But the two sciences are alike in that we retain something like matter nevertheless. St. Thomas calls this matter “intelligible matter.” For example, a triangle, being an accident, can only exist in a substance. But this substance, which is a sort of material for the shape, is not defined with sensible qualities like hot and cold. Mathematical things, then, are more abstract because they are more removed from the condition of the individual sensible things which we see around us. Nevertheless, here too we have both universal and particular – both the universal nature of triangle and this particular triangle. So mathematics, like natural philosophy, is about the universal and necessary natures abstracted from the particular matter, but the mathematical objects are yet more abstract or more removed from matter since they also leave sensible matter aside altogether.

The case of metaphysics is in a way a little easier to grasp. There are some things the definitions of which include no matter at all, neither sensible nor intelligible, neither common nor individuating. God and angels are purely spiritual beings and neither exist in nor are defined by matter. So too, “being” and “one” are found not only in material and mathematical things, but even in these immaterial things. Though being and one can exist in material things, they can also exist outside of material things. Consequently, being and one can be defined without sensible or intelligible matter.

There is a difference, though, in the way metaphysics is removed from matter and the way the two other sciences are. In math and natural philosophy, we ignore the matter in which our objects really do exist. We do not address the existence of mathematical objects in the material world one way or the other, we just ignore it. So too, we do not address the way physical things exist in particular instances, but sticking to universal claims, we ignore particular matter in its particularity. But in metaphysics we do not merely ignore matter but deny it. We say that our objects really are, or at least really can be, without any matter. For this reason, St. Thomas will speak of the removal of matter in metaphysics as a “separation” or a negative statement. We will, in other words, actually deny materiality of our objects, whereas in the other sciences we will simply not consider the matter from which we abstract.

So, to return to our main point, from the point of view of the power of knowing, namely, the mind, and from the point of view of the thing known, namely, the subject of science, we come to the same conclusion, that sciences are what they are by remotion or removal from matter – physics considers the natures of mobile beings but not their individual matter; mathematics considers natures which are found in matter but are defined without sensible matter; and metaphysics considers natures which are not defined with matter and which either may or do exist without matter. Since we should divide things by differences which are essential to them, and sciences are what they are by remotion from matter, we should divide the sciences by how they are more or less remote from matter.

We should take particular note that the division of the sciences is not in terms of mere generality. Just as there are particular plants which share the nature plant, so there are particular triangles which share the nature triangle. And just as biology is about the kind of thing a plant is in abstraction from individual plants, so mathematics is about the kind of thing a triangle is in abstraction from individual triangles. Nor are mathematics and natural science distinct because one is more universal than the other. Rather, they are distinct because the notion of matter enters their definitions in different ways, and so gives rise to different degrees of intelligibility. Thus, universality is found in all the sciences, so that the abstraction of the universal from the particular cannot be the unique mark of any one science nor, therefore, its defining characteristic.

So our second preliminary notion is that the sciences are distinguished by the way they define their subjects, with sensible matter, or without sensible matter but with intelligible matter, or without any matter at all.

 Given these preliminaries, we may ask how metaphysics begins. Is it necessary to prove the existence of purely immaterial beings before approaching metaphysics? Or can we understand things without any matter at all even without doing this? And if we do need to argue that such things exist, how can we do that?


Part II – Metaphysics is after Physics


Now, we might think we can just by-pass such an argument and go directly to metaphysics because St. Thomas will frequently describe the subject of metaphysics as “universal being” or “being as being.” This might lead one to think that there can be a distinct science of metaphysics simply because we have a name more universal name, “being.” Moreover, Aristotle even says that we should start with the more general, so metaphysics would not only be possible right away, but would be the very first philosophy we should study, perhaps after logic. The name “being” certainly does seem to name something more universal than the expression “mobile being,” which is the subject of natural philosophy – after all, the adjective “mobile” qualifies and limits the noun “being.” But we just saw that degrees of universality alone cannot define sciences, so this cannot be a path to metaphysics.

Moreover there may be an implicit assumption here, namely, that because there is no overt reference to matter in the meaning of “being,” one can immediately grasp that there is a science which transcends matter, one which studies being universally, without restricting itself to material being, and that therefore there is a science which has a new mode of definition. Take away “mobile” and we have left a “being” which does not depend on matter for its concept.

But this is a mistake. It is true that the meaning of the word “being” does not include an overt reference to matter, but it does not follow that there really is an immaterial being or even that we can really conceive of it, except as a quid nominis, in the same way that we can entertain the notion of a greatest prime number. As Aristotle says, “If … there is not some other substance besides those constituted by nature, physics would be the first science.” For the actual principles of being as such would simply be the principles of mobile being – there would be no new kind of thing to study, but at best a new set of names. If natural beings are all that can exist, then potency is simply reducible to matter and its consequences, act is correlative to matter, being is always and only the result of the union of such matter and such form, and unity is convertible with that sort of being. There would be no other principles but those of physical things; there would be neither any new subject to be understood nor any new principles, nor even any new way to understand the old principles.

Thus, it turns out that we may have been too generous when we said that the primitive notion of being was more general than the notion of mobile being. If there are no immaterial beings, then “being” is not really more general; it is just a more obscure and imperfect way of saying “mobile being.” On the other hand, if we treat being as if it were applicable to immaterial things without knowing the first thing about them, namely, that they exist, we would be resolving to a quid nominis of a mystery, a mystery about which we are not even assured that it is not merely the absurd expression of our own ignorance. We have already seen that proceeding on the grounds of terms like these is merely looking at an ens rationis, a being of reason, and that our propositions about them are never about reality but about the relations among our thoughts. If, armed with only such knowledge of the meaning of the name, I argue that angels, because they are immaterial, are individuated by their forms, I am no better off than if I argue that hobbits, because they are childlike, would be fit carriers of the ring of power, if there were such a ring. Both statements are true, in fact, though they have no bearing on reality and it’s silly to call these inferences “science.” They are true simply due to the relations between their antecedents and the consequents. The grounding of the antecedent, and so of the whole statement, in extra-mental reality would require that I know that angels or hobbits are actual things and not just figments of my imagination.

Thus, unless we can show somehow that immobile beings are really possible natures, metaphysics is only a fancy name for natural philosophy.

What is needed, then, for a new science is, first, a kind of definition that does not include matter as do the definitions of mathematics and physics, and, secondly, the knowledge that things so defined are possible natures. If we can establish that there are such real objects of thought, we will then know that the word “being” is not only more vague but even has wider application than mobile being, that it is truly more general than mobile being and that the treatment given to being, one, etc., in natural philosophy is not the most complete one possible. What are the possible routes to such knowledge? I suggest that there are four possibilities to consider, only one of which is an actual path to metaphysics.



Let me outline the four quickly. The first is brute experience. We know, e.g., that horses exist because we experience them: there is no need to investigate whether or not they exist. But we have by nature no such experience of immaterial things. Even the great St. Augustine, after all, said that for years he could not even conceive that incorporeal beings were possible, which he would hardly have claimed if the experience was a common one.


The Three Acts of the Mind

The other three possibilities arise from St. Thomas’ division of the acts of the mind into three sorts. The first act of the mind is the grasping of what a thing is, for example, what horse or circle is. This is a simple apprehension in which we only think one thing; we do not combine our thoughts to form statements or arguments. The second act unites the things grasped into statements: “the horse in an animal” or “the circle is not an animal.” Here we find the true and the false for the first time. But there is no proceeding from one truth to another. For this we need the third act of the mind. Here we put statements together into a third act of the mind, an argument: “The horse is an animal; the circle is not an animal; therefore, the circle is not a horse.” Here one statement, called the conclusion, is seen to follow from other statements, called premises. These three acts of the mind provide a helpful guide to possible routes into metaphysics. I will argue that the first two acts by themselves cannot lead to metaphysics but that the last, argumentation, and, in particular, argumentation within natural philosophy, is a real road to metaphysics.


The First Act of the Mind – Grasping Natures

To start then. Our second possible route to seeing that there are immaterial realities the first act of the mind. This is the route proposed by the medieval Arabic philosopher Avempace (Ibn Bajja). In the Summa Theologiae, St. Thomas reports that Avempace held that one could abstract from material things the essences of immaterial things. The argument goes like this: “For since our intellect is naturally apt to abstract the quiddity of a material thing from material, if in that quiddity there is again something material, it will be able to abstract again, and since this cannot go on to infinity, at length it will be able to arrive at understanding some quiddity which is wholly without matter. And this is to understand immaterial substance.”

St. Thomas’ critique of this view is pertinent not only to its refutation but also to our more general consideration. Here are his words:

This would be said efficaciously, if immaterial substance were the forms and species of these material things, as the Platonists posit. But if we do not posit this, but suppose that immaterial substances are of a wholly other notion from the quiddities of material things, however much our intellect might abstract the quiddity of a material thing from matter, it would never arrive at something similar to immaterial substance. And therefore we are not able to understand immaterial substances perfectly through material substances.


St. Thomas is saying that we cannot abstract the quiddity of an immaterial thing from a material thing for the very simple reason that it is not there in the material thing to begin with. If immaterial things are of a wholly other nature than material ones, then the notions we get from material things will never be the same as the notions of immaterial things. Thus, since abstraction is only the drawing away of one notion from another, we cannot arrive at the notions of immaterial things from material things by way of abstraction.

The upshot is that immaterial things are of such a profoundly different sort from material things that we cannot divine what they are by looking at what is present in material things. Because this is so, the names which we use of immaterial things and of material ones, like being, one, potency, act, and so on, are not univocal, but analogous. The only way they could be univocal is if the natures they named were the same, and if they were the same, then we could abstract the notion of an immaterial thing from a material thing. St. Thomas even says that the very name quiddity itself is equivocal when said of immaterial and material things: “quiddity and all such names are said somewhat equivocally of sensible things and of those (i.e., immaterial) substances.”

It is not obvious, then, from direct experience or from abstraction from direct experience, that immaterial substances can exist at all, since we do not have any actual contact with such things by way of our natural knowledge of material things. We cannot know them to be possible, as we have seen, simply by not seeing that they are impossible. That would be like saying that the diagonal of a square could be commensurable with its side just because I don’t see why it cannot be so. Not seeing a contradiction is not the same as seeing there is no contradiction and we often must go past the overt meaning of the words we use to see if there is contradiction or possibility or even necessity.


The Second Act of the Mind – Forming Statements

On to our third possibility, the second act of the intellect, forming judgements or making statements. Rather than think we either have direct experience of an immaterial thing or that we can abstract the nature of an immaterial thing from material things, we might think we can, based on our direct experience of the natural world, separate something which transcends matter from the material things in front of us. To quote the man who seems to be the originator of this view, Etienne Gilson:

What comes first is a sensible perception whose object is immediately known by our intellect as “being,” [ens] and this direct apprehension by a knowing subject immediately releases a twofold and complementary intellectual operation. First, the knowing subject apprehends what the given object is, next it judges that the object is, and this instantaneous recomposition of the existence of given objects with their essences merely acknowledges the actual structure of these objects.

The claim is that the mind seizes a being [ens], that is, “that which exists” or “what has existence” [quod habet esse], and this implies that the mind must see that something exists, which is to see the truth of a judgement. For in grasping the existent thing in front of us we grasp that it is a thing that exists, or, in other words, we grasp that the statement “being exists” is true. So immediately upon grasping the first object of the mind, we form the statement that something exists, and this is a judgement, a statement, not the simple abstraction of a nature. But in that judgement we grasp both the thing and its existence, and so we can separate in our minds the existence from the thing which enjoys that existence. Thus we form the negative judgement that the thing is not its existence. We recognize, according to the proponents of this theory that existence not identical to the material nature in which we recognize it. This negative judgement will then be used to distinguish the subject of metaphysics by claiming, in one way or another, that it shows the possibility of the existence of immaterial beings.

Those who agree up to here now go their separate ways. Jacques Maritain concludes that we have a grasp on the possibility of immaterial almost immediately upon our recognition of being, or as he famously called it, our “intuition of being:”

 Such objects [i.e., transcendentals, such as being, one, etc.] are trans-sensible. For though they are realized in the sensible in which we first grasp them, they are offered to the mind as transcending every genus and every category, and as able to be realized in subjects of a wholly other essence than those in which they are apprehended. It is extremely remarkable that being, the first object attained by our mind in things … bears within itself the sign that beings of another order than the sensible are thinkable and possible.

Elsewhere he is a little more explicit about how this occurs: “In other words, in the (unique) case of the intuition of being, the concept, this concept of the esse, formed after I have seen it, is second in respect to the judgment of existence where and in which, while pronouncing existence in itself, my intelligence has seen the esse. This concept is owing to a reflective return of simple apprehension upon the judicative act in question.”

Immediately after the first text I cited, Maritain adds that this is only the recognition of a possibility, that we would need to have some “reasoning from the data actually given to us in sensible existence” in order to know that there actually are such immaterial things in fact. Nevertheless, for Maritain the full latitude of the possibilities of being is immediately established and we are set to begin metaphysics.

Other followers of Gilson hold that, since existence is a separate intelligible object, not the same as the material essence it actualizes and so not in its very notion already material, we can judge by a separation that non-material being is possible. In other words, since we can distinguish between what a thing is and that it is, the question “what is it?” is not the same as the question “does it exist?,” and therefore the two questions can be addressed independently. The proponents of this position say that the notion of existence is intelligible without a consideration of what particular sort of thing is existing, so that, while existence is presented to us in material things, we can recognize that it need not be in material things. Thus, we have the separation from matter necessary to begin metaphysics. The separation, that is, the negative statement which grounds metaphysics, is not “some real thing is not material,” but rather something like, “existence is not a material essence.”

But however one analyses the claim that we are aware of the reality or even the possibility of immaterial beings based merely on what we see in our encounter with the material world, the claim cannot be true. Any such claim necessarily implies saying that the initial experience of the material world intrinsically contains (that is, not by way of an argument) a sufficient motive for thinking there can be immaterial being, and this is false. The judgement only shows us that material being is possible and real. The problem is the old one: we think because we see no problem that there is no problem, as if our intellect with its flickering light were the measure of all things. Because when I say “being is,” I do not seem to posit anything material, I think that I am thereby permitted to say that being or existence (ens or esse) can in fact be coherently thought of apart from matter. But the judgement in question only refers to the sort of being and existence we see in the material world; it says nothing whatever about any other sort of being. Unless we see an example of a certain sort of thing actually before us or else can prove that, given what do see actually before us, that sort of thing must exist, we may simply be mistaking ignorance for knowledge, mistaking our inability to see an absurdity with the absence of absurdity. To belabor a point, the fact that we do not see that a thing is impossible does not mean that we see that it is possible.

More particularly, it is a commonplace in St. Thomas that the existence of a material thing arises in some sense from the union of form and matter. A statue comes to be when a sculptor puts a shape into clay and a man comes to be when the soul is joined to the body. Whether one thinks this is all there is to it or one thinks that such a union is only presupposed to the existence of the material thing, it remains that existence in material things is intimately linked to the union of form and matter, that it is either the same thing as that union or is the act of what is so united. In either case, being and existence are said equivocally of material and immaterial being, so that the existence of material things is a really different sort of thing from the existence of immaterial things. So we cannot know, from seeing the sort found in the material, that the sort found in the immaterial is possible, let alone actual. When we remove from our notion one of the principles of material being and existence, namely matter, we may be left with nothing but a self-contradiction, though we might not be aware of the contradiction. I might as well say that because my first idea of water does not include hydrogen, I can have a science of hydrogen-free water.


The Third Act of the Mind – Argument

Since the evidence of things unseen, that is, the evidence for the immaterial, is not found in experience or in the first or second acts of the mind, it must, if it is available to us by nature at all, be found in the third act of the mind, namely, argument. But what sort of argument should we expect to find here? Our refutations of the other positions already point us toward the answer.

The argument in question must assure us of the real possibility of immaterial things. The problem with some of the views we have been considering is just that they assume the possibility of immaterial being based merely on the fact that they cannot see any impossibility. The insufficiency of these views indicates that we need to base our arguments on the knowledge of something which we know is really possible. But we only really know something is possible in one of two ways: either we see the thing in question in our experience or we see that what is in our experience necessarily implies the thing in question. Thus, if what we experience in sensation is really possible (which it obviously is, because it is actual), then what is implied by that experience is also necessarily really possible, in fact, it too must be actual. We must start with the material, mobile beings around us and, by way of an argument, prove that they could not be the way they are if immaterial beings did not exist. We must argue from the effects found in the natural world to the existence of their immaterial causes.

For we must begin from what we know and go to what we do not know and what we know first is the natural object of our mind. Because color is the proper, formal object of the eye, we see everything else by way of seeing color, as we see a motion by seeing color and a man by seeing color and a shape by seeing color. Following Aristotle, St. Thomas says that the proper object of the human mind is the quiddity of material things. If so, we cannot know anything except by way of knowing material things just as we cannot see anything except by way of seeing color. In the Commentary on the Sentences, St. Thomas writes: “…our intellect is not proportioned to knowing something by natural knowledge except through sensibles; and therefore it is not able to arrive at pure intelligibles except by arguing.” The arguments in question will end in negative judgements to the effect that this or that is not a material being, but their beginnings will be an understanding of the mobile things we directly experience.

Further, the arguments upon which we found our metaphysics will be based on causes which are outside of their effects. Some causes, such as matter and form, are inside the things they cause, as a man’s soul and his body are within him and are causes of him. But other sorts of causes are outside of their effects. Agent cause, final cause, and exemplar causes are like this. The blueprint the housebuilder uses, the purpose which motivates him to build the house, and the housebuilder himself are all extrinsic to the house he builds. These are the sorts of things we must look for, because we have seen that material things do not harbor immaterial being within them; this is precisely why all the other paths to metaphysics were discovered to be futile. We must find an argument which ties what is present within the material things around us to their extrinsic causes, which turn out to be the immaterial things we seek to know.

Moreover, the link must then be a necessary one: if it is not necessary, we will not begin our science with the certitude necessary for science, for knowing that the subject is real is a necessary precondition of a science. We are looking, then, for an demonstration which begins with some effect found in mobile beings and which shows us that that sort of effect necessarily implies the existence of an immaterial being.

Such an argument is proposed by Aristotle in the Physics. Aristotle there argues that there must be a first mover and that this first mover must have infinite power, and no body can have infinite power. We draw the negative conclusion, then, that the first mover is not material. This is the separation or negative judgement that St. Thomas has in mind when he says that what characterizes metaphysics is separation. He himself implies as much when he says, more than once, that those who have not discovered such an argument fail to attain the threshold of metaphysics.



The principle at work throughout this lecture has been this: act is before potency. If we are to come to know, the knowledge we seek must be based on some actual pre-existent knowledge. But our actual knowledge is originally knowledge of material things; this is implied by saying that the proper object of the human intellect is the quiddity of material things. Because the mind attains as its proper object the quiddity of material things, we know everything we know starting from those quiddities. Since the being of immaterial and material realities is only analogously, and therefore equivocally, one, we must get from the material to the immaterial by a necessary link, but one which appeals from what is actually present in material things to what is not so present; that is to say, a link which is founded on some form of extrinsic causality.

In other words, the only way to see the material as implying the immaterial is by recognizing that the material being needs immaterial principles or causes outside themselves. Neither the first nor the second act of the mind is sufficient for these only reveal what is actually present within the object named or spoken of; we need the third act of the mind, and in particular, arguments from effect to cause, to establish the reality of immaterial beings. Having seen that reality, we of course recognize that there are real immaterial natures to be considered, and once we see that we understand that there must be another science, more universal than natural science, the science of being as such.



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