Between " creation " and " commencement " : Georges Lemaître and the philosophical-theological debates surrounding the big bang

Questions raised by Georges Lemaître's intellectual and spiritual journey

The first phase of his itinerary

Marked by a phase of concordism, Lemaître sought to bring together physics and his reading of Scripture, marked by a fidelity to questionable exegetical injunctions given by the Pontifical Biblical Commission at the beginning of the ^20th century, in a context of reaction to the modernist current.

This early concordism was of course an epistemological error, and Lemaître resolutely abandoned it from 1929 onwards, following rather stormy interactions with Léon Bloy and encounters with Eddington and the Anglo-Saxon scientific world.

However, we can see that certain images from this concordist period (light as the essential and original foundation of all material reality) still provided him, between 1927 and 1930, with a kind of imaginary (but not conceptual, I insist!) background to guide him towards his "hypothesis of the primitive atom", that quantum of "radiation-matter", giving rise to all the "energy-matter" of our physical universe.

Second moment

Having arrived at the hypothesis of the primitive atom, completed by a model of a spherical relativistic universe with a positive cosmological constant and an initial singularity, he realizes that this hypothesis has perfect scientific autonomy. The beginning of the universe, for example, makes sense in and through physics, without any direct interference from metaphysics or theology. He thus secularizes the notion of the beginning of the universe, which becomes, for him, a "natural beginning", and at the same time adopts a position that we might describe today, following S.J. Gould, as one of "non-empiétement des Magistères", in other words of radical distinction between science and theology. His theory of "two paths to truth", also reminiscent of the Pascalian distinction between orders or the thesis defended by Pierre Duhem, goes hand in hand with a life that, with equal determination, pursues two solid commitments, one scientific and the other religious, in the unity of the same person but in two socially distinct spheres.

Lemaître is a deeply unified man on a personal level. However, he knows how to make epistemologically salutary distinctions. For him, at the end of the thirties, there can be no immediate conceptual link between science and theology. The unity of his science and his faith (intensely lived within a priestly fraternity known as the "Friends of Jesus", where secular priests took the vows proper to religious, including the vow of poverty) was based on personal life and action.

This secularization of the "natural beginning" was to reactivate classic philosophical debates: debates with neo-Thomists on the distinction between creation and beginning, on the possibility of an eternal yet created universe... but also Kantian debates, in the company of Ferdinand Gonseth, on overcoming the Kantian antinomies that prevented us from thinking, without contradiction, about the notions of temporal beginning and spatial limit of the Cosmos.

These debates are interesting, and demonstrate the relevance of a "two-way" interaction between science and philosophy. The results of physical cosmology show the limits of Kantian antinomies, but medieval philosophy has also helped us to understand that a theological notion of creation is not logically linked to that of a beginning. A world that owes its existence to God (i.e., a created world; creation being, for Thomas Aquinas, the metaphysical relationship by which God sustains the world in its being) need not have a finite past or future.

This clarification could have reassured cosmologists such as Bondi, Hoyle and Gold, who developed "steady-state cosmology" and rejected Lemaître's hypothesis, suspecting (wrongly) that the latter was involved in religious recuperation of cosmology. This clarification, combined with the fact that Lemaître's theory had not yet been validated (it would not be until 1965, with the discovery of the CMB), might also have tempered the enthusiasm of Pius XII, who, in his 1951 Un'Ora speech, ventured, without quoting its author, a comparison between the primitive atom and fiat lux... But this was not to be!

Third moment

When, at the end of his life, Lemaître had to talk about theological questions again, he seemed to fall back into a somewhat concordist language. In fact, this seems to be linked to something that can be seen in many contemporary believing scientists: the adoption of a radical separation, of the type recommended by S.J. Gould in his " NOMA principle "(Non Overlapping MAgisteria), is sometimes done by minimizing or forgetting certain conceptual difficulties. The search for perfect peace between the two fields can lead to the belief that all difficulties have disappeared. Yet difficulties often remain, stemming from the implicit or explicit constraints of coherence inevitably imposed by theological discourse on the philosophical discourse used to express it.

The epistemologically salutary distancing of science from theology is therefore not enough. Indeed, if we accept that there is a fruitful and inevitable interaction between science and philosophy, we also need to manage the relationship between philosophy and theology, in the knowledge that each theology is structured by philosophical presuppositions and that it induces constraints on the philosophical framework that are not negligible.

We could, of course, simplify the problem by simply annulling theology, but believing scientists like Duhem or Lemaître would be unable to accept this because of their deep-seated convictions. We could also deny the interactions between science and philosophy by reducing science to "saving phenomena", but science, it seems to us, carries a genuine "ontological charge". It explains, not merely describes, the structure of empirical reality. It is therefore inevitably open to a philosophical dimension.

This leads us to a hypothesis: the resurgence of concordism that can be found, despite their prudence, among great contemporary scientists, who are also deeply religious, could well be linked, not to a lack of distinction between science and theology - which they readily and rightly admit - but to an obliteration or underestimation of the constraints that a theology inevitably places, sometimes unwittingly, on their philosophy of nature (for, and this is the important point : not every philosophy of nature is compatible with every theology!). If these constraints are not correctly identified, this obliteration risks interfering with or once again creating damaging short-circuits in "science-theology" dialogues.