A few days before his death on June 20, 1966, the Belgian cosmologist Georges Lemaître heard from his collaborator Odon Godart of the discovery of the cosmic background radiation, the “fossil” radiation of the hot dense early phase of the universe. As the visitor recalled: “Despite being very sick, he [Lemaître] lucidly expressed his satisfaction regarding the discovery of a type of cosmic microwave radiation that seemed to confirm the idea of an explosive origin of the universe” (415).

Lemaître, born in 1894, has been one of the fathers of modern cosmology, contributing to the development of mathematical models for the universe based on Einstein's theory of general relativity. Though this should not be overemphasized, he is more specifically known for his imaginative terminology, “a primeval atom.” He was from the “pays noir,” the area were the coal mines were. After high school he entered a program that would have made him a mining engineer. He served on the allied side at the Belgian front in WWI, and returned to the university in 1919 to pursue mathematics and physics. A year later, he also entered the seminary to become a priest in the Roman Catholic Church. In his dissertation La physique d’ Einstein he discussed philosophical presuppositions as well as scientific issues. In 1923, he received grants to work in Cambridge, England, with Arthur Eddington, a British cosmologist, science communicator, and committed Quaker, as well as thereafter to make a trip to Canada and the United States, where he studied at Harvard. In his Harvard PhD thesis, he showed how solutions to the equations of general relativity as found by Einstein and by De Sitter could be considered two limiting cases of a more general class of models of the universe. In a subsequent article in 1927, in French, Lemaître derived a linear relation between the distance of a source and its recessional velocity, using data from Hubble to determine what nowadays has become known as the Hubble Constant—after Edwin Hubble who two years later, not knowing of Lemaître's work, published more data supporting this linear relationship. After Eddington learned of Lemaître's paper in 1930, an English translation of Lemaître's paper was published—but without the computation on the expansion rate based on the data available in 1927, because Hubble had more accurate data in his 1929 publication.

In addition to his life as a scientist, which is also of serious interest in the period after the 1920s, Lemaître was a priest. In an interview in New York Times Magazine in 1933, he defended the coexistence of religious and scientific perspectives as complementary paths, with different aims. Biblical passages need not be taken literally (211):

But the Bible says creation was accomplished in six days, you protest. “Isn't that a direct, literal statement?”

“What of it?” retorts the priest. “There is no reason to abandon the Bible because we now believe that it took perhaps ten thousand million years to create what we think is the universe. Genesis simply tries to teach us that one day in seven should be devoted to rest, worship and reverence—all [of] which are necessary for salvation.”

For Lemaître, all his scientific work, including the speculative work on a primeval atom, is metaphysically neutral. “It leaves the materialist free to deny any transcendental Being. … For the believer, it removes any attempts to familiarity with God. … It is consonant with Isaias speaking of the ‘hidden God,’ hidden even at the beginning of creation” (Notes for a lecture in 1958; see 332).

Distinguishing the two had been his position all those years, but for “materialists,” including Fred Hoyle and Russian cosmologists, he remained a Roman Catholic priest whose scientific work was suspect of bias by an interest in proving creation. And, sadly enough, Catholic authorities had used modern cosmology in this way. In a speech to the Pontifical Academy of Sciences on November 22, 1951, Pope Pius XII said: “Indeed, it seems that the science of today by going back in one leap millions of centuries, has succeeded in being a witness to that primordial Fiat Lux, when out of nothing, there burst forth along with matter a sea of light and radiation” (quoted at 338). Lemaître was one of the members of the Academy present at that speech. Lemaître never criticized the Pope publicly, but from other sources it seems clear that he was not too happy about the conflation of scientific and metaphysical issues. Let me add a source Lambert seems to have missed. In the paper “How Should Cosmology Relate to Theology?,” often seen as the paper that introduced the notion of “consonance” in the modern religion and science discourse (a word I saw in this biography also in writings of Lemaître), Ernan McMullin—himself a priest and philosopher of science—discusses the papal address of 1951. McMullin was a student in Leuven (Louvain), Belgium, at that time. McMullin (, 53 n25) adds a footnote of which I quote here the initial lines.

The present writer [i.e., McMullin] was attending a graduate seminar with Lemaître in 1951, and can recall very vividly Lemaître storming into class on his return from the Academy meeting in Rome, his usual jocularity entirely missing. He was emphatic in his insistence that the Big Bang model was still very tentative, and further that one could not exclude the possibility of a previous cosmic stage of contraction. Lemaître was not mentioned in the Pope's speech, though a member of the Academy. It was said at the time that the principal author of the speech was Fr. Augustini Gemelli, a Franciscan priest‐psychologist from Milan on whom the Pope frequently relied in matters scientific.

Lambert does not mention Gemelli in this context, but as the first president of the Pontifical Academy he does appear in his study at various places. Lemaître succeeded him in 1960 as the second president of the Academy, broadening its horizon, adding more non‐Catholic scientists including seven Nobel laureates, and initiating study weeks on a wide range of topics.

This is merely a limited sample of the rich and detailed information in the biography written by Dominque Lambert. This biography of Lemaître was published initially in French in 1999. It has been translated for this edition by Luc Ampleman and edited by Karl von Bibber, who have done an excellent job. There is a preface by P. J. E. Peebles and an afterword by Michael Heller, relating the work of Lemaître to developments and orientations that continue to be most relevant. However, most praise should go to Dominique Lambert of the University of Namur, Belgium, for drawing extensively on archives and scientific papers to bring us a biography of this major scientist, who was also a priest and thus had to reflect on the philosophical issues involved in the co‐existence of these two languages and disciplines.