Gauvain Leconte-Chevillard

The notion of emergence in philosophy is standardly taken to perform the metaphysical task of accommodating leveled structure: a 'vertical' relation between levels that explains the co-temporal dependence and novelty of e.g. biological entities with respect to their physical particles (life emerges from Carbon in the sense that it depends on Carbon atoms, but has a sort of higher-level autonomy). However, many authors have alternatively argued for a diachronic notion of emergence, where the relation is 'horizontal' in the sense that it is between same-level, but temporally successive, states. Wilson (2024) has recently put forward a challenge: what is the difference between diachronic emergence and causation? If there is no difference in the metaphysical task performed, there is no reason to take diachronic emergence seriously. In this paper, we show that there are at least two (non-mutually exclusive) different ways to characterize diachronic emergence as a determinative relation clearly distinct from causation: the first criterion is epistemic (with ontological import), the second is strictly ontological. We also provide concrete examples from the philosophy of science and show cases of the fruitfulness of this metaphysical notion.

This paper is meant to offer a better understanding of the philosophical view called 'powers ontology' and its relevance to science. After briefly discussing on the one hand the intuitive pull of dispositional notions and their application in science (micro-physics in particular), and on the other hand the metaphysical and epistemological issues typically arising from the application of powers in science, we defend a dynamic notion of the dispositional essence, where the individuation of the power does not the depend on the manifestations brought about by a certain activity, nor the stimulus conditions enabling such activity, but on the very activity itself. In the last part of the paper, we discuss two cases of theoretical unification in early 20th century physics: Einstein’s equivalence principle and de Broglie wave-particle duality principle. We show how a powers ontology, intended in the sense described above, would be able to elegantly account for how these unifications were achieved and why they were successful.

La réalisation de prédictions précises et surprenantes est une pratique essentielle des sciences empiriques et la confirmation de ces prédictions semble représenter l’un de leurs principaux succès théoriques et pratiques. Ainsi de nombreuses scientifiques et épistémologues attribuent-ils aux succès prédictifs le pouvoir de confirmer des hypothèses, d’influencer le cours de l’histoire scientifique, voire de révéler quelles théories reflètent la réalité. Pourtant les prédictions s’appuient souvent sur des représentations simplifiées, idéalisées ou fictionnelles de la réalité. L’objectif de cette thèse est d’analyser l’activité prédictive pour comprendre en quoi consistent les succès prédictifs et quelle portée on peut légitimement leur conférer. L’enjeu de cette analyse est notamment de savoir si une théorie ayant engendré un succès prédictif peut être considérée comme vraie ou partiellement vraie. La première partie de la thèse est consacrée à l’analyse de l’activité prédictive et conclut qu’il existe une pluralité de raisonnements et de succès prédictifs. La deuxième partie étudie l’influence de ces succès sur l’évolution d’une discipline, la cosmologie, de 1917 à nos jours et montre que les scientifiques attribuent de l’importance aux prédictions qui indiquent la capacité prédictive d’une hypothèse ou d’une théorie. Dans la troisième partie, je soutiens que le rôle des prédictions dans le choix rationnel des hypothèses est de permettre de juger de leur fécondité. La quatrième partie étudie les limites de la portée des succès prédictifs en montrant qu’ils ne permettent pas de savoir quels aspects des théories dont ils sont issus reflètent la réalité.

En 2016, peu de temps après l’annonce de la première détection directe des ondes gravitationnelles qui avaient été prédites par la théorie de la relativité générale un siècle plus tôt, un panneau « Told you so » fut retrouvé suspendu à la statue d’Einstein de l’université Georgia Tech. Les prédictions réussies frappent l’imagination du public comme des experts : elles semblent constituer l’un des plus hauts accomplissements scientifiques et l’une des preuves les plus tangibles de la fiabilité et de la vérité de nos meilleures théories. Et pourtant les philosophes des sciences n’ont accordé que peu d’attention à la définition et à l’histoire des prédictions scientifiques. Cet ouvrage regroupe plusieurs essais portant chacun sur un cas ou plusieurs cas de prédictions ayant réussi (et parfois échoué) dans différentes disciplines scientifiques allant de la mécanique céleste à la climatologie. Chaque cas permet d’aborder un problème philosophique spécifique tel que : « Est-ce que les scientifiques ne prédisent que le futur ? », « Un succès prédictif peut-il déclencher ou mettre fin à une révolution scientifique ? » ou « Peut-on considérer qu’une théorie qui a prédit avec succès un phénomène inconnu est vraie ou approximativement vraie ? » L’enjeu de ces questions est non seulement d’explorer la structure et la portée de l’activité prédictive des sciences modernes, mais aussi de comprendre comment ces succès et échecs prédictifs peuvent servir l’information scientifique du public et des débats démocratiques.

La cosmologie, la science de l’Univers en tant que structure globale des phénomènes physiques, est un domaine animé de nombreuses controverses non seulement scientifiques mais aussi philosophiques. Cet ouvrage examine cinq périodes de l’histoire de la cosmologie physique depuis 1917 et étudie les débats qui ont porté sur l’expansion de l’Univers, sa forme, son évolution, ses premiers instants et l’existence d’univers multiples. Chacun de ces débats a soulevé de nombreux problèmes épistémologiques, tels que le problème de l’induction, celui de la démarcation entre science et pseudo-science, celui des hypothèses ad hoc ou de la sous-détermination empirique des théories scientifiques. On montre comment les cosmologistes ont participé à ces controverses, l’impact que celles-ci ont eu sur le développement historique de la cosmologie et les enseignements que peut en tirer la philosophie des sciences. Cosmology, the science of the Universe as the encompassing structure of all physical phenomena, is a vividly debated topic at both a scientific and a philosophical level. This book investigates five periods of the history of physical cosmology since 1917 and examines the controversies on the expansion of the Universe, its form, its evolution, its beginning and the existence of multiple universes. Each controversy has raised several philosophical issues, such as the problem of induction, the question of demarcation between science and pseudo-science, the status of ad hoc hypotheses or the underdetermination of scientific theories by empirical data. We show how cosmologists participated in these debates, how they impacted theory-change in cosmology and what philosophy of science can draw from it.

According to the leading hypothesis in primordial cosmology, the very early universe underwent a rapid phase of accelerated expansion known as cosmological inflation. Inflation ended approximately 10^{−34} s after the expansion began, through a process called reheating, during which the inflaton field decayed into the particles of the Standard Model. In this paper, we do not address questions concerning the empirical adequacy of this cosmological scenario. Instead, we focus on two following questions: 1. According to inflationary cosmology, can we argue that the particles of the Standard Model emerged from the inflaton field, and in what sense? 2. If we claim that the interaction carriers of the Standard Model (e.g., gluons) emerged during reheating, does this imply that the laws governing these interactions (e.g., the strong nuclear force) emerged at the same time? We argue that current models of reheating already provide a clear answer to the first question when interpreted through a diachronic account of emergence. However, the second question may not have a definitive answer, as it depends on one’s metaphysical conception of physical laws. We propose that a powers ontology, according to which laws are based on the causal profile of fundamental dispositional properties, could elegantly accommodate the claim that physical laws emerged in the wake of inflation.

Among physicists and cosmologists, it is common practice to refer to the "cosmic laboratory" to describe how the study of the universe others important insights into the inner constitution of matter. Yakov Zel'dovich, for instance, famously claimed that the "universe is the poor man's accelerator." The goal of this paper is to clarify the relationship between cosmology and particle physics by examining a case of crucial importance in connecting these fields: how cosmologists of the 1970s were able to limit the number of lepton families from the measure of the cosmic abundance of helium-4 . My claim is that knowledge of the primordial universe enables cosmologists to conceive it as a natural experiment for testing hypotheses of particle physics, thereby supporting the analogy between the universe and particle colliders.

According to a defense of scientific realism known as the “divide et impera move”, mature scientific theories enjoying predictive success are partially true. This paper investigates a paradigmatic historical case: the prediction, based on Fresnel’s wave theory of light, that a bright spot should figure in the shadow of a disc. Two different derivations of this prediction have been given by both Poisson and Fresnel. I argue that the details of these derivations highlight two problems of indispensability arguments, which state that only the indispensable constituents of this success are worthy of belief and retained through theory-change. The first problem is that, contrary to a common claim, Fresnel’s integrals are not needed to predict the bright spot phenomenon. The second problem is that the hypotheses shared by to these two derivations include problematic idealizations. I claim that this example leads us to be skeptical about which aspects of our current theories are worthy of belief.

It may seem impossible to apply Ian Hacking's experimental argument for scientific realism to astrophysical objects; indeed Hacking himself expressed scepticism about extra-galactic entities (Hacking 1989). Such astrophysical antirealism has been vividly debated and is usually seen as an undesired consequence of experimental realism. In this paper, I claim that it is possible to rephrase the experimental argument with James Woodward's non-anthropocentric account of experimentation (Woodward 2003) to apply it to some astrophysical entities, such as gravitational lenses. I also argue that this new formulation of the experimental argument solves several problems of Hacking's original version.