The Symbiosis of Science and Metaphysics

Stephen Barr Faith Magazine November – December 2010

Stephen Barr argues that the reticence of the Thomistic tradition to allow modern science to affect metaphysics has been an own goal. He is a member of the First Things'editorial board and is professor of physics at the University of Delaware. He is author of Modern Physics and Ancient Faithand A Student's Guide to Natural Science.

Might the discoveries of modern science have implications for theology? They certainly cannot alter the substance of "the faith once delivered to the saints". They can, however, affect our cosmological and philosophical ideas and thus change the way we conceive of certain religious truths. To take an obvious example, even though the Church had no teaching on the location of Hell, it was once generally supposed by theologians to be somewhere inside the earth. Today this view would strike most Christians as extremely implausible, if not absurd. This is not a question of a change in doctrine, but of a change in "World Picture", to use a term of the Polish physicist and philosopher Fr. Michat Heller.

In every age, people naturally form World Pictures that are syntheses of ideas derived from various sources - prevailing scientific theories, philosophical speculation, revealed truth, widely accepted notions, and "common sense". In this way, non-theological currents of thought, including scientific ones, inevitably and often unconsciously influence the ideas of theologians. Clearly, there is a danger of theologians becoming too wedded to current, and possibly transient, scientific theories. But, as Fr. Heller notes, it is also risky for theologians simply to ignore scientific developments, as many do, for they may then unwittingly retain in their thinking elements of older, scientifically obsolete World Pictures. There are no simple rules here; discernment and prudence are required.

A set of issues of much contemporary interest where these considerations apply concerns the resurrection of the dead. One strand of tradition emphasises the continuity of the "world to come" with this world. It is de fide Catholic teaching that we shall rise with the "same bodies" we now have, and most theologians have understood this to mean that our resurrected bodies will be composed of the "same matter" as composes our present bodies. Indeed, a recent book even suggests that they must contain some of the very same particles. Quite other considerations, such as concern for the environment and reaction against what some see as too otherworldly a faith, have led to greater emphasis recently on the idea that the physical universe and the earth itself will be redeemed and renewed.("[T]he creation itself will be set free from its bondage to decay and obtain the glorious liberty of the sons of God. " Romans 8:21.).

This is an area where modern science has definite things to say. First, it is absolutely certain that the earth will be obliterated in about 5 billion years, when the sun becomes a red giant star. And in the standard cosmological theory of today, the universe will either end in a "Big Crunch", in which time itself will end, or will continue to expand forever, becoming ever colder, darker and more empty, and eventually losing all capacity to sustain life. It would seem, then, that the "new heavens and new earth" of which Scripture speaks must be truly new creations rather than mere modifications of the present heavens and earth. This is entirely in accord with the numerous scripture passages that speak of heaven and earth passing away and being destroyed utterly, even to the dissolution ofthe elements.

Second, the idea that resurrected bodies will share some of the very same individual particles as our present bodies is actually inconsistent with theoretical particle physics, which says that elementary particles (such as electrons) have no individuality at all. (In the physics literature this is called the "quantum indistinguishability of particles". It has generated much discussion among philosophers on the lack of "haecceitas" of elementary particles. This is an excellent example, incidentally, of something that will be discussed below, namely how science can be relevant to fundamental issues in metaphysics, in this case whether "matter individuates form" as Aristotelian/Thomistic metaphysics asserts.)

Third, the "bondage to decay" of the present creation is rooted in a very fundamental feature of the laws of physics of this universe called the Second Law of Thermodynamics. A world not subject to decay would have to obey such radically different principles that it is very doubtful that it could be seen as in physical continuity with this universe. Of course, our imaginations are limited and God is omnipotent. But, as these three points show, any theological conception of the world to come that posits a strong physical continuity with the present world faces formidable theoretical difficulties coming from physics. I should note that one theologian whose writings on bodily resurrection and eschatology show a sophisticated awareness of some of the implications of modernphysics is Joseph Ratzinger.

A second set of theological issues to which the discoveries of modern physics are relevant concerns the nature of time. The traditional view, most profoundly developed by St. Augustine in the eleventh chapter of his Confessions, is that time is a feature of the created world, and so is itself something created. This implies, as St. Augustine first pointed out, that it is quite meaningless to speak of a "time before creation". The beginning of the created world must be the beginning of time itself. Einstein's theory of gravity (General Relativity) leads to the same conclusion by a parallel route. According to General Relativity, the space-time manifold is a physical entity - it bends, ripples, expands and contracts, has energy, and interacts with other physical entities. For thisreason modern physics also affirms that the beginning of the physical universe is the beginning of time and space. St. Augustine's deep reflections in this area led Bertrand Russell to praise his "admirable relativistic theory of time", and Steven Weinberg has noted that "it seems to have become a tradition to quote from [Augustine's Confessions] in writing about quantum cosmology."

A second implication of St. Augustine's insight is that God in his own nature (as distinct from the finite human nature assumed by the Word) must be outside of space and time. Created things, at least those that are part of this physical universe, have among themselves spatio-temporal relations; but God dwells in "the sublimity of an ever-present eternity", the "nunc stans" (the now that stands still) and knows and wills all things by a single atemporal act.

Strangely, there has been a movement away from St. Augustine's profound conception. One sees this in certain forms of process theology and "kenotic" theology, and quite definitely in "open theism". Open theism argues that God does not know "the future", either because it does not yet exist to be known, or because God chooses not to know it, in an act of kenosis (self-emptying). This is supposed to give creatures greater freedom. What is ironic is that these "modern" theological trends do not comport very well with what modern science has learned about time. Since space-time is now known to be something physical, to suppose the divine nature bound to the time of this world is perforce to suppose God a physical being locatable in space - a remarkably primitive notion.

Newtonian physics projected the simple one-dimensional timeline of our mental experience onto the physical universe. Special relativity showed, however, that space-time has a more subtle four-dimensional structure, in which it does not make sense to speak of the past, the present, or the future of the universe as a whole. What is past, present, or future to one point of space-time does not coincide with what is past, present or future to a point spatially distant from it. If it was naive to project our one-dimensional mental timeline onto the universe, how much more so to suppose that it could be projected onto the Mind of God, who infinitely transcends the universe.

Beyond directly theological issues, does modern physics have anything to say to metaphysics, and therefore indirectly to theology? Some might argue not, on the grounds that metaphysics speaks about such general features of reality - of being as being - that it cannot be affected by discoveries of particular contingent facts about the world. And yet, Aristotelian metaphysics, which has such an important place in Catholic thought, was not conceived in isolation from scientific investigation. Aristotle was himself a great scientist and both his metaphysics and science make use of the same technical apparatus of form, matter, substance, accident, potency, act, and so on. Indeed, it was largely as a theory of nature that Aristotelianism first commended itself to medieval Christianthinkers.

It is a great problem that traditional Aristotelian/Thomistic metaphysics and modern science no longer speak the same language, as they did in the Middle Ages. Indeed, there are many terms and concepts in the language of each that are now almost untranslatable into the language of the other. Some argue that this is the fault of modern science, which restricted its attention to a limited range of questions having to do with the merely quantitative aspects of things and with efficient and material causes at the expense of formal and final causes. While there is some truth in this, it is only a part of the story. The language of Aristotelian/Thomistic metaphysics has changed very little since the advent of modern science and its vocabulary seems from a scientific perspective quite stiltedand awkward for many purposes.

Physics has had enormous success in explaining why things happen as they do in the natural world, but its modes of explanation do not fit neatly into the four-fold classification of material, formal, efficient, and final causes. For example, when physicists explain the electrical conductivity of metals in terms of the "band structure" of the energy levels of the electrons in a crystal lattice of atoms, to which of the four causes does that correspond? As this example illustrates, explanation in modern physics is almost entirely in terms of mathematical structure and involves an enormously rich set of ideas about form. The fact that modern science is nonetheless typically accused by Aristotelian/Thomistic metaphysicians of neglecting "formal cause" shows that they are working with adifferent notion of form than are contemporary physicists and mathematicians. In Aristotelian/Thomistic philosophy, the ideas of formal causation and substantial form have a teleological thrust that is largely missing from the physicist's conception of form, which corresponds more to Lonergan's broader idea of form as "intelligible structure".

Another example of a linguistic/conceptual difference between Aristotelian thought and modern science is that the former usually envisions the action of one thing upon another (for example fire heating iron), whereas in modern physics the physical world is explained in terms of mutual "interactions". A third example is that the notions of "species" in Aristotelian philosophy and modern biology are not compatible. Aristotelian species are what mathematicians call "equivalence classes", so that if A is of the same species as B, and B is of the same species as C, then A must be of the same species as C. However, it does not appear possible in biology to define species in a way that always satisfies this condition. (The existence of "ring species", such as the Larus gulls,illustrates the problem, as indeed does "speciation" in evolution, whereby all animals are of the same species as their parents and offspring, but not as their remote ancestors or descendents.)

In short, Aristotelian/Thomistic philosophy has paid a heavy price for the two and a half centuries in which it largely ignored what was going on in the natural sciences. A sustained re-engagement with science would enrich its conceptual and linguistic resources. This re-engagement cannot simply be an attempt to translate statements of modern science into existing Aristotelian terms. That cannot be done in many cases. Rather, many more Aristotelian/ Thomistic metaphysicians than currently do must learn to listen to and understand science in its own native tongue. Modern physics has made discoveries (e.g. quantum mechanics) which undoubtedly have profound metaphysical implications, but what those implications are cannot be explored unless the physics is understood directly and not "intranslation".