How Thomists View the Modern Sciences

Debates concerning the existence of God typically run aground on prior unresolved metaphysical questions. Any debate with a Thomist about the existence of God turns into an exposition of a number of metaphysical notions – potentiality, actuality, matter, form, essence, existence, motion, cause, and effect.

Skeptics tend to quickly recognize that they are not only being asked to accept the existence of God, but an entire metaphysics. Often enough, the effect is not only a continuing disbelief in God, but an even greater incredulity towards Thomist metaphysics.

If the skeptic is asked not only to believe in an ultimate ground of the universe (i.e., God), but also that the universe is explained by philosophers rather than scientists, they may rightfully decide that the theists premises are more absurd than their conclusions.

This article takes up the question just what metaphysical principles skeptics ought to be asked to accept in the context of arguments for God's existence. Our particular focus concerns the relation between Aristotelian-Thomist metaphysics and the modern empirical sciences. Our contention will be that the modern empirical sciences presuppose a latent Aristotelian-Thomist metaphysics, and that the history of science verifies the core contentions of Aristotle and St. Thomas. Our approach follows that of the great 20th century philosopher, Bernard Lonergan.

We grant, however, that certain forms of Aristotelian-Thomist metaphysics have put themselves in opposition to the sciences by supposing that in addition to the forms of physical things which the empirical sciences grasp, there are also intelligible forms grasped either by the metaphysician or by the ordinary person. For example, in addition to the form of the tulip grasped by the plant biologist, some would assert another form accessible either to the philosopher qua philosopher, or to human beings by virtue of common sense. However, we reject this view as both incompatible with the sciences and mistaking the nature of metaphysics.

We will conclude that matter, form, and existence; act and potency; substance and accident; and being are known tacitly (or operationally) by the empirical sciences and that one cannot be a scientific realist and reject these metaphysical notions.

1. Matter and Form

All human knowledge begins with something unknown to us. What are the celestial bodies? Why do things fall to the ground? How is it that plants grow? Why do we get sick? The empirical sciences provide answers to these "what", "how", and "why" questions.

The march of the sciences follows a predictable cycle.

Level 1: Experience. First, we encounter something we do not understand. This could be the experience of water freezing and melting, observations of retrograde motion, the distribution of prime numbers, or plotted data reported from a particle accelerator.

Level 2: Understanding. Second, we seek to understand by getting a better look, reframing the problem, performing thought experiments, proposing new theorems, etc. That is to say, we formulate possible explanations. We do not simply seek more facts, we seek more facts insofar as they may prompt a Eureka moment that explains a set of facts. We do not seek more data for its own sake, we are after an insight that may be suggested by the data.

Matter and form correspond to experience and understanding in the course of explaining the physical universe. That is, matter corresponds to what is known by scientific observation as needing explanation. Form corresponds to what the scientist articulates as a possible explanation of the data.

The positive role of metaphysics is not to establish particular scientific answers (forms), but primarily to reflect upon the regular, general structure of scientific knowledge, and secondarily on the history and discoveries of the sciences, in order to discover their universal structure and significance.

2. Common sense and scientific understanding

The distinctions between matter and form, representation and understanding demarcate the sensible and the intelligible. Insofar as something is visible or tangible, sensible or imaginable, it remains on the first level. Aristotle distinguishes sensible and intelligible form. Insofar as something may be sensed or imagined, it remains on the level of experience. Conversely, insofar as something is understood, it cannot be seen or imagined.

Take, for example, the triangle. Can one imagine a triangle? Although we can call to mind a triangular shape, one cannot actually imagine a triangle. For a triangle is composed of lines and vertices which have no breadth. But a line or point which has no breadth is visually indistinguishable from emptiness.

Or take mass. Weight corresponds to something feeling heavy or light. But how heavy or light something feels depends on the bodies around it. Mass is classically defined not in relation to the experience of heaviness or lightness, but in relation to force and acceleration. Were it defined in relation to an experienced quality such as heaviness or lightness it could not explain those qualities. That is to say, it is not a descriptive term, but an explanatory term. Explanatory terms are not directly related to any particular sensible experience, but to other terms in an abstract, theoretical framework such as classical mechanics or general relativity.

This distinction between descriptive and explanatory terms corresponds to the levels of experience and understanding. Insofar as a term is descriptive, it is defined in terms (at least partly) of what is sensed or experienced. Explanatory terms cannot presuppose the experiences they are supposed to explain, and so they are abstract. Heaviness is descriptive, mass is explanatory. "Hot" is descriptive; temperature is explanatory. "Fast" is a descriptive term, while acceleration and velocity are explanatory. Six feet tall is descriptive; a thing's coordinates in Minkowski space are explanatory.

The Aristotelian notion of intelligible form displaces the world of common sense. The things we thought most familiar to us become quite strange. The ability to pick out everyday objects such as water, trees, or cows does not grasp what these things really are. In the Aristotelian terminology, when we teach a child "this is the color red" or "this is a cow, and that a horse", we are offering merely nominal definitions. We are explaining the use of words, not the natures of things. We are merely associating words with sensible similarities or family resemblences, we are not understanding things as they are in themselves. Animals, after all, are able to distinguish roses from replicas. But the reality of things is hidden to them precisely because they cannot construct abstract explanatory schemas.

3. Essence and Existence

From the limitations of mere understanding enters the notion of existence. Early modern scientists proposed the existence of an aether to explain the propagation of light. It was a sensible enough idea – it was coherent and had explanatory power – but it turned out not to actually exist. The question of essence and existence, then, is the question of whether what possibly explains the data (i.e., concepts, theories) actually does so, or whether it can be supplanted by a better explanation. Thus, to use the Aristotelian terminology, essence (meaning primarily form) is related to existence as potency to act.

This leads to the notion of pure act – that is, God. If for limited minds essences relate to existence as potency to act (because there is the question whether a more comprehensive act of understanding could displace the current theory), it is possible to hypothesize a complete act of understanding which, as complete, cannot be revised. The primary content of that act of knowledge would be, by definition, purely actual. And that pure actuality is, of course, God. But as yet, this is merely a hypothetical limit case.

4. The full picture

The full picture, then, of the metaphysical elements looks like this

Mental operationProgressionMetaphysical Element
ExperienceSense perception -> experience -> imagination, measurementMatter
UnderstandingInsight (aha!) -> definition, formulation in general theoryForm
JudgmentDetermine conditions -> weigh evidence -> affirmationExistence

Were we to the complete scientific explanation of our universe, we have three distinct components: that which is grasped in the data as needing explanation (i.e., the matter), that which is grasped initially by an insight and articulated in an abstract theoretical framework which would explain the data (i.e., the form), and that the fact that possible explanation on the second level in fact does explain the data and will not be replaced by a more adequate explanation (i.e., existence).

This division is irrefutable. For insofar as scientists have something to inquire into, insofar as they hypothesize explanations, and insofar as they settle which explanations are sound, they operate on the level of experience, understanding, and judgment. Insofar as knowledge is empirical, scientists must engage all three levels. And insofar as scientific inquiry reaches its objective, there is a component to be known by experience (matter), understanding (form), and judgment (existence).

5. The Existence of God

We have seen that, in the empirical world, scientific realism commits us to the view that things are composed of matter, form, and existence. There is nothing to a thing above what is captured in these categories. The particular content that fills out each of these categories is to be determined by the relevant particular sciences.

Moreover, we have seen that the more general categories of potentiality and actuality apply to matter-form-act composites. If something is merely an aggregate of lower level events, if there is nothing that answers the question "why isn't this just an aggregate explained by lower-level categories?", then there is not a thing but an aggregate of things. Put differently, if there is nothing to understand, there is nothing. (Which is why there cannot be paranormal phenomena without an explanation.)

As matter is what is able to be explained by form, so form is what can explain underlying materials. But just because something could be an explanation does not mean that it is in fact an explanation. To do that, one must identify the conditions which, if satisfied, would render the explanation final. Grasping form as actual, not merely possible, is necessary for a complete act of knowledge. Thus, form, of itself, is in potentiality to existence.

Our purpose has been to show that the metaphysical categories employed by Thomists in arguing for the existence of God are not abstruse philosophical matters, but necessary if empirical sciences can get at the truth. Though their names are perhaps foreign, they are defined in relation to familiar cognitional operations.

To the objection that some Thomists have supposed that formal causes are not the provinces of the sciences, I will simply quote with approval Bernard Lonergan's assessment:

One takes the descriptive conception of sensible contents, and without any effort to understand them, on asks for their metaphysical equivalents. One bypasses the scientific theory of color or sound, for after all it is merely a theory and, at best, probable; one insists on the evidence of red, green, and blue, of shapr and flat; and one leaps to a set of objective forms without realizing that the meaning of form is what will be known when the informed object is understood.

Such blind leaping is inimical not only to science, but to understanding.

So the extent that Thomists wish to lecture scientists on to the "true" nature of time and space, I happily concede that they are not only not advancing understanding of the natural world, but they are misconceiving the nature and role of metaphysics.

I have not addressed the actual arguments for the existence of God. Those arguments have not been made here. However, the basic categories which they suppose cannot be rejected without rejecting science as knowledge. The validity of the basic terms have been established. Physical things are composed of matter, form, and actuality. Immaterial things, if they exist, lack the material component. Non-divine immaterial things can be understood via distinct acts of understanding and judgment, and so they are composed of form and actuality. God, on the other hand, is the primary content of a single act of unrestricted act of understanding, which – it turns out – cannot be distinguished from that act of understanding.

How Thomists View the Modern Sciences