How are Physics and Metaphysics Related?
John M. McDermott SJ FAITH Magazine November – December 2010
John M. McDermott SJ argues that matter and man exhibit a transcendence of universal formality and intelligible reasoning. This points to the need for a metaphysics that uncovers the fundamental realms of freedom and love. Fr McDermott is a faculty member of the Sacred Heart Major Seminary, Detroit. Since 2003 he has served as a member of the International Theological Commission, and since 2008 as a consultant to the USCCB Committee on Doctrine.
The question finds a facile answer: metaphysics comes after physics. Greek meta means "after", and Aristotle's early commentators aligned the Metaphysics after the Physics. But that ordering finds a deeper reason. Physics studies space, time, and motion. Greek physis denotes a nature, a principle of motion and rest. Motion is inherent to worldly natures because they are composed of matter and form. Form provides the intelligible principle which can be grasped in universal abstractions, while matter indicates the principle of individuality, what makes natures this or that particular instance of a species or genus. A polar tension exists between form and matter since neither can be reduced to the other but both essentially constituteevery material reality. The tension inherent in this diversity in unity underlies many others. "Substance" is often used as the equivalent of "nature", yet substance denotes what remains the same in accidental change, e.g., although a man changes in size, weight, position, age, etc., he remains substantially the same man. So from different perspectives the same reality is seen as a dynamic nature and a static substance. This holds true since the abstract form of the substance-nature remains always the same, yet in its concrete instantiations the form always seeks to realise itself more adequately. As by nature an acorn seeks to become a full-grown oak and a chick strives to become a chicken, so a human being is oriented by inherent natural dynamism to full self-realisation. As long asform and matter are joined motion seeks its completion in rest.
To study motion Aristotle identified four causes. A cause answers the question "why", giving the reason for something. "Why?" can be answered variously. "Why is something such as it is?" calls for a formal cause; e.g., "dogginess" makes a dog a dog. "Why this rather than that?" seeks a material cause. "Why is it moving?" can aim at discovering a final cause, the goal or "that for whose sake" something moves. So the chick desires to become the best chicken possible - a natural final cause - or a man chooses the purpose of free action. The same question might also seek an efficient cause, defined as the primary principle of motion and rest. It applies to both the motion imparted from without by contact and the motion internally generated by a self-moving nature. Indeed nature and efficientcause overlap since both are principles of motion. The nature's form actively seeks its realisation, thus acting as an efficient cause. Moreover, since that same desire orients the nature to a determined goal - a chick cannot become a horse - and in a sense anticipates it, formal and final causes also coalesce.
The only cause which cannot be equated with another is the material cause. While matter serves as the ultimate principle of continuity in substantial change - e.g., the form of grass is replaced by the form of the cow digesting it but the material component of grass subsists under the form beefsteak- matter is not ultimately intelligible because it cannot be grasped in universal concepts. This resistance to the mind's attempts at order creates a problem. Truth consists in the conformity of mind and reality (being) - if the human mind cannot know reality, thinking is senseless - but the mind cannot grasp individuality as such. Hence Aristotle considered (prime) matter to be unintelligible and non-being. Furthermore, since matter cannot be grasped in a finite form, it is infinite. Lest theuniverse become irrational, Aristotle contained matter within form; the universe is finite with the highest heaven containing all mobile realities beneath it. Nonetheless, since matter is unintelligible, it allows for contingency and chance: although one can explain why individual causal chains occur, e.g., why treasure is buried in a field and why a farmer ploughs his field, it is inexplicable why here and now, while ploughing, the farmer hits upon buried treasure.
Zeno's paradoxes also manifest matter's unintelligibility. As Parmenides' disciple, Zeno defended spiritual monism by showing that all attempts to understand space, time, and motion involve contradictions. For example, if space is continuous, to cross a stadium one must traverse the space's entirety; but to go all the way, one must first go half-way, then half-way again, ad infinitum; since a spatial line contains an infinity of points, it is impossible to arrive at the stadium's other end. Yet the initial measurement of the stadium's length involved distinguishing one portion of space from another, i.e., considering space discontinuous. A contrary example presupposes that space is discontinuous. Imagine an arrow fully occupying a space equal to its own dimensions; since thearrow cannot pass from one spatial position to another, space being discontinuous, the space of the arrow must move with it
from one point to another in a series of discontinuous "jumps" until it arrives at its destination. But to remain within its own space fulfills the definition of a reality at rest; hence the arrow in motion is always at rest. Nonetheless, some spatial continuity exists; otherwise the arrow's space could not transfer itself from one position to another. A final example concerns a material whole divisible into ever smaller parts; since the process of division can be continued to infinity, one never attains the smallest unity. Without a unity, however, a multiplicity, i.e., a collection of unities, cannot be recognised. Hence there is neither "one" nor "many." This ridiculous conclusion is contradicted by the presupposition of the initial material whole, a unity. When Aristotle declaredmatter, the basis of space, time, and motion, unintelligible, he finessed such contradictions.
Matter allows for motion, yet matter is unintelligible. Consequently, the ultimate intelligibility of motion cannot be found in motion. The universe's intelligibility must consist in a reality transcending matter as pure form. Aristotle's argument for a First Mover in Physics VI appealed to efficient causality: a stone is moved by a stick, moved by a hand, moved by the man. Since an infinite regress is unintelligible - just as matter's infinity is unintelligible -but motion must be intelligible lest reality be senseless, a First Mover must exist. He cannot be composed of matter. He is pure Form, separated from the material universe, like a Platonic form which Aristotle otherwise rejected. Metaphysics XII employed a similar argument but relied ultimately on finalcausality: the First Mover moves the universe as the goal of motion: "He moves by being loved." Thus physical motion is explained by a reality beyond motion: metaphysics transcends physics.
Plotinus later employed Aristotle's First Mover as the goal of motion and also ascribed to Him, the One, an active emanation whereby all of reality, even prime matter, flows from Him before turning back to Him. Since matter, infinite non-being, derives from the One and finds its final intelligibility in Him, the One is infinite. Yet God exercises no act of volition or intellection lest duality taint pure Oneness. Although Plotinus insisted that the One's emanation is beyond necessity, his doctrine conduces to pantheism.
Christianity's doctrine of creation introduced new meaning to metaphysics since God's free act simultaneously distinguishes Him from created realities and assures His love of them. Aquinas clarified the doctrine by identifying God, the First Mover, with infinite Existence (Esse) and then distinguishing essences ("what something is", the equivalent of nature-substance) from existence in created realities. Therefore all beings are contingent in their very existence. But for God's will they need not be. His infinity explains the infinity in created individuals insofar as His creative act makes everything. Though human minds cannot grasp individuality, the infinite God knows individual existences thoroughly. Hence material reality is intelligible even as its intelligibilitytranscends human rationality. Yet, given God's love of creation, there is an analogy between human knowing and God's knowing: despite all differences between infinite and finite, men can approximate God's mind and know something of God and creatures. Thus physics, the knowledge of finite mobile realities, again demands something beyond physics for complete intelligibility.
Newtonian physics placed this metaphysical view into question when it regarded nature as inert mass, i.e., dead matter, moved from without by efficient causality. Final causality was excluded even though gravity, the attraction of one body upon another, remained a mystery. God's existence was required to explain motion's original impetus and prevent certain irregularities from devolving into chaos. Later Laplace succeeded at subsuming Newton's irregularities under laws. Physics began to serve again as the paradigmatic science. Chemistry was assimilated to it and its method of analysis and explication was applied to biology and humanistic "sciences" like economics, psychology, and sociology. Philosophy suffered from physics' hegemony since empiricists reduced knowledge to sense impressionswhile idealists sought necessary universal laws through the analysis of ideas. Finally Kant banished metaphysics from the realm of objective science because, unlike physics, it deals with realities not perceptible to the senses. "Objective science" occurs only when the mind's categories are joined to sense impressions to produce Newton's universal, necessary laws.
With physics dominating the end of the nineteenth century; scientific determinism was widely preached: since physical laws are necessarily and universally valid, nothing escapes them. Contrary to experience, with ideological consistency philosophers denied moral freedom and biological finality. Admittedly an underlying problem exists: if thought's laws are not arbitrary, they must be necessary. The laws of contradiction and sufficient reason should apply in all cases. Hence reality contains necessities corresponding to mental laws. Whereas classical philosophy grounded such laws in natures, but restricted their application insofar as matter introduces contingency, nineteenth-century physics subjected material realities to inviolable law.
Fortunately other philosophers realised that physical laws consist of abstractions and reality surpasses abstractions. Almost simultaneously physicists encountered conundrums overthrowing the Newtonian world-view. Electrons and photons manifest themselves as both continuous waves and discontinuous particles. Ever smaller particles-waves are postulated. Time and space are made relative to motion. The universe is conceived as infinitely expanded in three dimensions (Newton) and as a four-dimensional, limited space-time continuum (Einstein) and as a congeries of discontinuous spatial events occurring when gamma-rays strike electrons (Heisenberg). Since sub-atomic realities cannot be known apart from scientists' active interventions which change the direction and speed of the electronstudied, Heisenberg held that reality is unknowable and can only be approximated. Zenonian paradoxes reappear to reopen Western thought to metaphysics and freedom.
While some philosophers, acclaiming human reason's inability to know reality, equate freedom with arbitrary choice, urging others to "create their own values", such immorality soon runs into contradictions. If abstractive reason always falls short of reality, philosophy degenerates into mindless chatter and reality soon teaches the wayward the price paid for irrationality. Recurring patterns exist in reality, which physical laws approximate. So men can generally foresee the consequences of actions. But the commitment which moral behaviour demands, doing good for its own sake, surpasses all rational calculation. Every finite reason offered can be questioned and relativised from a different perspective, until one recognises that moral obligation is previous to rational abstraction. We donot choose to be born but finds ourselves thrust into life with obligations to parents and others. We are summoned to commit ourselves absolutely to do the good even to death, but only God's call can ground absolute commitment. Hence an adequate metaphysics must transcend the finite, recurring patterns of natures to deal with freedom and God. Although various metaphysics have been excogitated, history has shown that physics cannot justify itself because the material realities with which it studies contain paradoxes requiring a suprasensible, indeed, an infinite grounding. Another science must speak the last word after physics.
In a forthcoming issue we plan to publish a piece by Fr McDermott on evolution and a discussion upon it with us.
 For farther developments of these points cf. our "Faith, Reason, and Freedom", Irish Theological Quarterly 67 (2002), 307-332; "The Mystery of Freedom", Lateranum 1A (2008), 493-542; "Why Matter Matters", Proceedings of the Sixty-Seventh Annual Meeting of the Jesuit Philosophical Association, ed. J. Koterski (New York: Fordham, 2006), 19-47.