AuthorTitleitle.dotAuthorTitlePUP UserBonnie202009-03-16T19:11:00Z2009-03-16T19:11:00Z1201211471Princeton University Press95261345711.0000 On physics and theology Bernard d'EspagnatI understand that, in the spirit of this workshop, I should speak on the possible relationships between physics and theology or, more generally, metaphysics. Which, of course, implies going to the roots of what contemporary physics really is. This is all the more necessary as the views on which contemporary physics actually rests are very much at variance both with those of old time physics (called classical physics) and, I would say, with "commonsense" ones. At the beginning - in Galileo's time - physicists thought that the description of the physical world should be grounded on just a few basic notions, such as position, shape, motion, and force, called "primary qualities". These notions are so familiar and look so simple that they were taken to be obviously valid. And it was considered that the ultimate aim of physics was to combine them quantitatively, so as to describe the complexity of the world as it really is. It is interesting to note that for a long time this idea was extremely fruitful. Nay, still today, in most fields of study the scientist feels satisfied when and only when he has succeeded in reducing complex data to things and events described by means of such clear, familiar concepts. Indeed, in the eyes of most scientists scientific research basically resembles what young boys experience when they open some old watch and try to understand how it works. They realize that this working is complex and that understanding-it requires much thinking. But still, in their quest one thing is simple: they do not have to build up the concepts they will ultimately need. Cogged wheels are solid objects and mankind always had the notion of solid objects. The same is true concerning the contact forces exerted by one cog on another one, and so on. In most scientific disciplines the same is true. In them the investigated objects are complex ones but at the end of an often intricate chain of arguments the scientist generally succeeds in producing - in terms of "simple and familiar concepts" - an account of their behavior that he deems satisfactory. No wonder that the specialists of these disciplines tend to consider that everything that physically exists is ultimately describable in terms of the said familiar concepts.Now, one of the most important and less controversial messages of contemporary physics is that this view is quite definitely erroneous. In a move that was slow at first but progressively speeded up, physics taught us, not only that the human mind is able to operate well outside the framework of familiar concepts, but also that it absolutely must do so. To give you just one simple example: physics definitely shows that no tiny thing - think of an electron, say - can be thought, when not observed, to be at some definite place and subjected to merely distance decreasing forces. The idea that what exists - the Universe - is basically constituted of elements you can refer to using common words therefore crumbles down. Indeed, as Hervé Zwirn noted:“It would seem that, for the first time in the history of philosophy, choosing to believe in the existence of a world both external to all observers and roughly consonant with what we perceive has become impossible, short of taking up an irrational standpoint”.For metaphysics the importance of this finding is considerable. Formerly, matter-of-fact people - opposed to metaphysics - used to say: "Since, in principle, everything is ultimately describable by means of simple familiar, day-to-day concepts, why on earth should we take interest in metaphysical constructions based on quite different notions?" Clearly, this criticism falls outside the marks when it is shown that for doing research the physicist has to work much outside the framework of familiar concepts.Admittedly, at this stage people will say: OK, to describe the foundations of the outside world we shall drop our familiar concepts and turn to the new, scientific theories, called the standard model, superstring theory, etc.. But there a surprise comes. All of these theories are based on the basic principles of a ground theory called standard quantum mechanics; and when we look carefully at the said principles we discover that they involve us in a basic way. I mean: contrary to those of classical physics, they are not descriptive: they are merely predictive of observation. Consequently, when these contemporary theories are interpreted as yielding descriptions of what exists, as is done in popular books, this interpretation may only be viewed as as metaphor. In truth, what these theories do yield is but a set of predictive rules concerning outcomes of planned measurements.From all this it follows that, most presumably, science will never disclose to mankind ultimate reality as it really is. Its true role is to synthesize our common, communicable experience. It is worthwhile to note that this confirms a view that Henri Poincaré put forward more than a century ago when he wrote (in La science et l'hypothèse) that the real objects will remain eternally hidden to us.But then, Ultimate Reality is what? As you see, great questions of perennial philosophy, which many used to consider obsolete, are reopened by present-day physics. But they are reopened without, of course, acquired knowledge being wiped out. And in particular, this acquired knowledge has just showed us that simple, elementary ideas just do not work. We therefore must exert caution.It is true that for maximal caution we might thing of resorting to the philosophical axiom: "what we are not - and never shall be - able to talk about is to be considered nonexistent." But the idealist and positivist philosophers who implicitly apply this axiom seem to me to be overlooking the fact that the scientific rules of prediction of observation work fantastically well. I, for one, am unable to convince myself that this perduring success is a miracle. I therefore believe that it has a general cause, that is, some basic Reality that underlies all these predictive rules and whose, known or unknown, features somehow cause them to work. On the other hand, as we just saw, this basic reality cannot be taken to be constituted of countless tiny elements, as philosophical atomic theory would have it. Nay, apparently - for reasons we, unfortunately, have no time to go into here - basic reality is not even susceptible of being conceptualized in any credible way. Indeed, in this respect it shows some affinity with Plotinus' basic notion of the One, which is totally unknowable but from which every existing thing emanates.So, as you see, contemporary physics has it it elements of such a nature as to suggest to metaphysicians interesting problems and fields of study. Will these problems meet with some of those of theology? The fact that (as we saw) physics strongly suggests that Ultimate Reality is both unitary and beyond the range of ordinary human experience speaks for a positive answer. But when we come to details we observe that the kind of Ultimate Reality physics makes us think of is not equally consonant with all types of theology. Clearly it does not harmonize well with the widespread conception of a "fully existing" God creating or having created "fully existing" objects. For this implies that, for example, an electron, once created, exists "by itself". Whereas, as we saw, physics shows that an electron is but an element of the representation we build up of Ultimate Reality. To some extent the message from modern physics seems to me to be more consonant with Saint Augustine's views, for Augustine claimed that our sensations do not passively reproduce the external world as it really is. On the contrary, he held that we are the ones who impart to them their detailed features. Clearly there is some similarity between this view and the fact that we are the ones who interpret our experimental results in terms of a concept "electron" that we have constructed. But, I think, what counts most within the philosophical message of contemporary physics is that, as we saw, science does not enable us to build up any credible, faithful representation of whatever could be termed "basic" or "ultimate" reality. In this respect the said message is clearly similar to the one issuing from "negative theology". And, though I am not a theologian, I would like to tell you in a few minutes about my own personal reflections concerning the said similarity.As most of you know, negative or "apophatic" theology is the doctrine that stresses that God is so very much above us that there is no point in attributing to Him features or qualities similar to our owns. One of its main advocate was Dionysius called "the Areopagite", a christian neoplatonist who more or less identified God with the Plotinus' notion of the One that I just mentioned. In particular, same as in Plotinus' doctrine, in Dionysius' negative theology, mind, soul and material things - in short everything that exists in the World - are successive emanations from the said One. In that sense the World is a creation of God, same as in Judeo-christianism, and indeed during the Middle-Ages many jewish and christian theologians more or less adopted such a line of thought. On the other hand, creation through emanation is an idea that substantially differs from the usual conception of creation viewed as an act of will performed by a person, God, Who is a being creating other beings. For that reason Dionysius' views were criticized by other theologians as being pantheistic. As subtly making God something immanent to the World. Whether or not this criticism is justified concerning Dionysius' doctrine I leave theologians to decide. But it seems to me that anyhow the conception that I consider to be emerging from contemporary physics - that is, the one I sketched here - can be made free from it. More precisely I claim that it is both consistent and free from the criticism in question if we assume moreover (in line with Dionysius) that mind is a Plotinus-like emanation of God. For, in accordance with contemporary physics (and with Augustine's conceptions), we must consider that the elements composing the things (electrons and so on), hence the things themselves, hence the World, far from being self-existing entities, are just images that we construct. So that it is obvious that Ultimate Reality cannot be immanent to them.There is however another criticism that was recurrently addressed in the past to the Dionysius theory and that, a priori, might conceivably also be addressed to the physics-inspired conception I sketched. It is grounded on the fact that Dionysius did not (and could not) remain strictly in line with Plotinus' doctrine. According to the Plotinus doctrine, the One is totally beyond anything that we can conceive. It is totally unknowable and unreachable except perhaps (for a very few people!) through ecstasy. With Dionysius and his followers basically the same holds true. But then, are we compelled to deny that God can be subject to affection or capable of love? This distressing view would appear to contradict the whole authority of the Scriptures, and of course Dionysius did not assert it. In fact what he claimed is that no characteristics applicable to the finite and limited can be strictly applicable to the infinite and eternal and that therefore, strictly speaking God is not endowed with goodness… but still He is is endowed with "Super-Goodness", which (we must understand) is somehow "in line" with goodness; and same for truth etc. Not unsurprisingly, more recent theologians submitted this view to criticism. As befits the issue, their criticisms were subtle but still, roughly speaking it may be asserted that they centered on a simple logical argument: Either Super-Goodness is undefinable, and the statement that God is endowed with Super-Goodness has no meaning, or Super-Goodness is something analogous to the goodness we know of, and then we do (approximately) know something about God, contrary to the original claim.A priori a similar criticism might of course be directed to the physics-inspired conception we have been considering: Is there any point in grounding an explanation of phenomena on the notion of an Ultimate Reality that cannot even be conceptualized? In Poincaré's book there is however a hint at the way this difficulty might conceivably be overcome. Indeed, at the place where Poincaré stated that the real objects will remain eternally hidden from us he also claimed that science discloses to us the relationships they have with one another. Within present-day physics this might be interpreted to mean that at least such entities as the great universal constants, Planck's constant and the like, are elements of Ultimate Reality. And such a view is not at variance with the impossibility of conceptualizing Ultimate Reality since bare knowledge of such constants is not akin to a knowledge grounded on concepts, and obviously does not enable us to build up even a most vague and approximate representation of Ultimate Reality. Does this remark yield a clue for removing the similar difficulty concerning negative theology that we met with? Frankly I do not know, but I think the question is worth being investigated. So let me propose it to you as an example of possible relationships between research in science and research in theology.