Science et philosophie chez Henri Tintant (1918–2002)

Abstract

Henri Tintant played a pioneering role in the introduction of quantitative methods in palaeontology. Correlatively, he was always concerned by the question whether palaeontology was a science in the strong sense of the term, that is to say a kind of knowledge based on robust and lawful generalizations. This is the question that led him to develop philosophical thoughts in his published work. Although Tintant philosophical culture was wide, and probably rather (because of his social and religious commitments), it is only late in his career that he introduced explicit philosophical references in his published work. With the exception of one reference in 1978, all explicit philosophical references appear after 1983 (this is the year when he retired). These references are not very numerous. Most of the philosophical (or historical) literature quoted by Tintant shared the characteristic of bearing on the question of time, and more especially on the difficulties raised by this notion in science and history. In fact, Tintant did not come to epistemology on the basis of a bookish culture (although he had read a lot of literature). He came to it through his own scientific practice, and on the occasion of a critical reflection over the conceptual problems raised by the use of the species concept in palaeontology. For quite a long time, Tintant diffused Simpson's “evolutionary” definition of the species ( i.e: a lineage evolving separately, with its own role and its own unitary evolutionary role and tendencies). But in the 1960s, he began being quite critical about this concept, or, more precisely, about the criterion that Simpson had advocated for identifying “evolutionary species” as distinct from other species within a same lineage. The Simpsonian criterion consisted in saying that a given evolving population can be considered as a new species provided that it deviates from a previous related population at least as much as two good synchronic species of the same group would do. This, Tintant finally said, was “a purely gratuitous procedure” (Devillers et Tintant, 1996 : p. 120). This being said, the problem of what evolutionary species consisted in remained open. Tintant tried to overcome the difficulty with the aid of an epistemological analysis. For him, the evolutionary species concept, as well as the biological species concept, relied on a criterion of “relation”: descent in the first case, interfertility in the second case. But whereas interfertility “closes the species on itself”, the criterion of descent is an “open criterion”, which leaves room for creativity and contingency. In the last part of his life, when he had enough time for the development of his philosophical reflection, Tintant elaborated a rather precise epistemological interpretation of the status of evolutionary theory. The key notions of this general interpretation are the following. First he emphasized the irreversibility of evolution, not at the level of characters (repetition and return are common), but at the level of organisms. For Tintant, this was a well established general fact, which could not be contested. The second (and most important) notion consisted in the distinction between “laws” and “events”. Tintant supported the absolute priority of events over laws in the field of evolution. For him, there was no hope to unify the entire field of biological evolution on the basis of one or even several general laws. The historicity of evolution was thus radical. The third notion is a consequence of this thesis: Tintant emphasized the importance of chance and contingency at all levels of description of the evolutionary process. The thesis of the radical historicity of evolution also led Tintant to refuse the adaptationist stance of the Modern Synthesis, and to introduce a subtle distinction between “adaptation” (which results from natural selection) and “innovation” (unpredictable mergence of new properties, which Tintant considered as “the motor of evolution”. Finally, Tintant supported more or less consciously a general concept of science that can be considered as positivist. For him, laws were only “general facts”, and theories consisted in establishing a relationship between “general facts” and “particular facts”. Natural selection, for instance, was a “general fact” (rather than a theoretical principle). Charles Devillers's and Henri Tintant's common book published in 1996 bears testimony of the whole array of Tintant's epistemological reflection upon evolution. Although this book was a general presentation of evolutionary theory for young students, it contains the clearest and most systematic presentation of Tintant's epistemological contributions.