Physics & Metascience (Metaphysics)

George Mason University physicist (and author of The Theory of Almost Everything) Robert Oerter, discussing act in potency in in physics, writes "it seems to me that the concepts of time and change are metaphysically prior to those of potentiality."

My response:

The French physicist, philosopher and historian of physics Pierre Duhem would agree with you, Dr. Oerter, that physical theories do not depend upon a choice of metaphysics. Duhem masterfully shows this, with many historical examples, in his classic philosophy of science work The Aim and Structure of Physical Theory (excerpt). He also treats this in "Physics & Metaphysics," "Physics of a Believer," and this excerpt from To Save the Phenomena.

His reply:

Thanks, that's very helpful. From the second link:

"That Physics Logically Precedes Metaphysics

...We cannot come to know the essence of things except insofar as that essence is the cause and foundation for phenomena and the laws that govern them. The study of phenomena and laws must therefore precede the investigation of causes."

That's what I was groping for in my attempts to answer Feser.

However, I think there's a distinction that must be made between the metaphysical essences that Duhem is talking about and the metaphysical principles that Feser is talking about. Don't we need concepts of cause and change before we can even begin a physical investigation?

My response:

Your question appears to be a question on the method and division of the sciences. Boethius, following Aristotle, proposed that the "Speculative sciences may be divided into three kinds: physics, mathematics, and metaphysics.":

1. Physics [(the natural sciences)] deals with that which is in motion and material [(ens mobile or "mobile being")].
2. Mathematics deals with that which is material and not in motion [(∵ mathematical objects, or "mathematicals," do not move or change)].
3. Metascience deals with that which is not in motion nor material.

(cf. §II of his De Trinitate)

In this context, Thomas Aquinas writes in his Division and methods of the sciences, a commentary on Boethius's De Trinitate questions V and VI (my adapted translation follows):

q. 5 a. 1 objection 9: That science on which others depend must be prior to them. Now all the other sciences depend on metascience because it is its business to prove their principles. Therefore Boethius should have placed metascience before the others.

reply to objection 9: Although metascience is by nature the first of all the sciences, with respect to us the other sciences come before it. For as Avicenna says, the position of metascience is that it be learned after the natural sciences, which explain many things used by metascience, such as generation, corruption, motion, and the like [(e.g., actuality, potentiality, matter, form, etc.)]. It should also be learned after mathematics […]. […] Nor is there necessarily a vicious circle because metascience presupposes conclusions proved in the other sciences while it itself proves their principles. For the principles that another science (such as natural philosophy) takes from first philosophy [(i.e., from metascience)] do not prove the points which the first philosopher [(metascientist)] takes from the natural philosopher, but they are proved through other self-evident principles. Similarly, the first philosopher does not prove the principles he gives the natural philosopher by principles he receives from him, but by other self-evident principles. So there is no vicious circle in their definitions. Moreover, the sensible effects on which the demonstrations of natural science are based are more evident to us in the beginning. But when we come to know the first causes through them, these causes will reveal to us the reason for the effects, from which they were proved by a demonstration quia [(i.e., a demonstration a posteriori, a demonstration from effects to causes)]. In this way natural science also contributes something to metascience, and nevertheless it is metascience that explains its principles. That is why Boethius places metascience last, because it is the last relative to us (quoad nos).

See The Way toward Wisdom by Benedict Ashley (read the first chapter, this excerpt, John Deely's review). His main theses are that:

1. the natural sciences are epistemologically prior to metaphysics  
2. metaphysics, which he proposes we term "metascience," is the true philosophy of science.

Mathematical Nominalism vs. Mathematical Realism

From the comments to the posting here:

Of course we want to hear about mathematics!

You should do some posts on Thomism and mathematics. The literature out there on St. Thomas's conception of mathematics seems very sparse. I especially would like to see some studies of how a Thomist views calculus, infinitesimals, etc.

There are some things, for example: My quotes of St. Thomas on mathematics; ch. 6 of Mullahy's Thomism & Mathematical Physics (PDF pgs. 264 ff.) is entitled "The Nature of Mathematical Abstraction"; "A neglected Thomistic text on the foundation of mathematics" by Armand A Maurer; and St. Thomas on the object of geometry by Vincent Edward Smith. These are all online for free.

Also, if you don't know about Augustin-Louis Cauchy, read this Dictionary of Scientific Biography article on him. I quote it: "More concepts and theorems have been named for Cauchy than for any other mathematician (in elasticity alone there are sixteen concepts and theorems named for Cauchy)." In his Cours d'Analyse, he proved the Fundamental Theorems of Calculus and Algebra, described partial fraction decomposition, devised convergence tests, and was the first to devise the ε-δ formulation of the limit (cf. this article by a prominent Cauchy historian; I love how it begins! A proper understanding of calculus is absolutely vital for understanding the power and limits of modern mathematical physics.). Of course Cauchy is also famous for complex integrals. Since he was a devout Catholic, I've been wondering if he was well-versed in Thomism. He studied classics before becoming a mathematician, so it's possible. I'm not sure he wrote any treatise on the philosophy of mathematics, though.

My follow-up:

Definitely read St. Thomas's In Boethium De Trinitate, q. 5, a. 3: "Does Mathematics Treat, Without Motion and Matter, of What Exists in Matter?". (Questions 5 and 6 of In Boethium De Trinitate are also called St. Thomas's Division and Methods of the Sciences.) Cf. also St. Thomas's commentary In II Phys. lect. 3.

From what I have read, it seems that Aristotelian philosophy of mathematics does well making sense of the everyday mathematics your average person on the street uses, e.g. arithmetic, combinatorics, geometry, and other discrete disciplines.

Aristotle and St. Thomas certainly distinguished discrete and continuous quantity (cf. Summa I q. 3 a. 3: "punctum non est principium nisi quantitatis continuae, et unitas quantitatis discretae": "a point is the principle of continuous quantity alone; and unity, of discontinuous quantity").

However, like you say, it would be interesting to see if an account of infinitesimals, calculus, the larger infinities, etc. could be given, while remaining a realist (rather than nominalist) theory of mathematics.

St. Thomas, in his commentary on Aristotle's Physics, deals very well with the "mathematical nominalist objection" to actual infinities in nature (be they infinitely large {cardinalities of Cantor sets}, infinitely small {infinitesimals}, etc.): From In III Phys. lect. 7:

[...] [Aristotle] says that it is impossible for the infinite to be separated from sensible things, in such a way that the infinite should be something existing of itself, as the Platonists laid down. For if the infinite is laid down as something separated, either it has a certain quantity (namely, continuous, which is size [magnitudo], or discrete, which is number [multitudo]), or not. If it is a substance without either the accident of size or that of number, then the infinite must be indivisible—since whatever is divisible is either number or size. But if something is indivisible, it will not be infinite except in the first way, namely, as something is called “infinite” [viz., "not finite"] which is not by nature susceptible to being passed through [better translation: "which is not surpass-able"], in the same way that a sound is said to be “invisible” [as not being by nature susceptible to being seen], but this is not what is intended in the present inquiry concerning the infinite, nor by those who laid down the infinite. For they did not intend to lay down the infinite as something indivisible, but as something that could not be passed through, i.e., as being susceptible to such, but with the passage having no completion.

So, it appears the mathematical nominalists are correct when it comes to mathematicals indirectly "separated [abstracted] from sensible things" (e.g., ∞, א, irrationals, etc., which are only ens rationis, "beings of reason" or "mind-dependent beings"), but they are incorrect in claiming that mathematicals of discrete (e.g., the number 2) and continuous quantity (e.g., a regular dodecahedron) can only be ens rationis (or our names of those ens rationis). The issue boils down to whether or not actual infinities exist in nature (cf., e.g., the whole Physics lecture above or the Summa questions: "Whether an actually infinite magnitude [magnitudo] can exist?" and "Whether an infinite multitude [multitudo] can exist?").

Also, Pierre Duhem—an early 20th century French, Catholic, Thomist physicist, philosopher of physics, and founder of the discipline of the history of medieval physics—wrote, contrary to Poincaré, that mathematical induction can be reduced to a finite syllogistic process.

Happy Easter!