Michel Ghins

In this paper, I briefly present the regularity and necessity views and assess their difficulties. I construe scientific laws as universal propositions satisfied by empirically successful scientific models and made — approximately — true by the real systems represented, albeit partially, by these models. I also conceive a scientific theory as a set of models together with a set of propositions, some of which are laws. A scientific law is a universal proposition or statement that belongs to a scientific theory. Scientific laws also are laws of nature since we can provide arguments in favour of natural causal powers that ground the truth of laws. I argue that the truth of counterfactual conditional statements and the occurrence of regularities in nature provide good reasons to believe that real causal powers exist in nature and that the truth of scientific laws is based on a metaphysics of nature

L’opposition d’Ernst Mach à l’existence de l’espace absolu et à celle des atomes fait partie des lieux communs de l’histoire de la philosophie des sciences. Mais cette opposition est souvent exagérée et, de plus, mal comprise. La plupart du temps, son attitude anti-réaliste en ce qui concerne l’espace absolu, les atomes et les entités théoriques en général est interprétée comme une conséquence immédiate de sa position empiriste, parfois qualifiée de « sensationnaliste »ii. Cette idée reçue (défendue entre autres par John Blackmore [1972]) sur les thèses de Mach en matière d’épistémologie - et j’entends par ce terme d’épistémologie une conception philosophique de la connaissance en général (Erkenntnislehre) et pas seulement de la connaissance scientifique - comporte une grande part de vérité. Mais une part de vérité seulement. En réalité, les objections soulevées par Mach contre une interprétation réaliste des théories scientifiques – et qui sont moins radicales qu’on ne le pense habituellement – reposent également sur des considérations méthodologiques qui relèvent davantage de la philosophie des sciences (Wissenschaftlehre). On verra d’ailleurs que la pensée de Mach montre une grande cohérence, et même une continuité, entre sa philosophie de la connaissance d’une part, et sa philosophie de la connaissance ordinaire et des sciences d’autre part. Je présenterai d’abord les traits saillants des positions de Mach en ce qui concerne la connaissance humaine en général; ensuite, j’examinerai ses objections à l’encontre de l’espace absolu et, de façon plus détaillée, celles soulevées contre les atomes. Je me pencherai enfin sur les relations entre ces objections et sa prise de position empiriste. Cette analyse nous permettra de mieux comprendre la nature exacte de l’antiréalisme de Mach. Je tenterai de montrer que Mach peut être qualifié – même si cela peut paraître surprenant - de « réaliste scientifique » dans la mesure où certaines entités théoriques possèdent le même statut d’existence, prise en un sens faible, que les objets ordinaires.

In this paper I argue in favour of a moderate and selective version of scientific realism with respect to the existence of some physical theoretical objects and the truth of some statements about them. The analysis of common sense or ordinary experience reveals that existence and truth assertions concerning familiar objects are warranted if they satisfy what we call the criteria of presence and invariance. Ordinary objects exemplify a form or a structure determined by constant and changing features with respect to the variation of the conditions of observation and a content given in sensory presence. It is claimed that some theoretical physical objects that possess a structure or a form determined by invariant and variable characteristics relatively to a specified group of transformations and a content provided by observations on which the measurement of those characteristics is grounded can also be justifiably asserted to exist. We further show that this defence of scientific realism in physics doesn't fall prey to the objections that have been raised against the usual vindication of scientific realism based on the no-miracle argument. Some standard objections to scientific realism, such as the underdetermination of theories by observations and the pessimistic meta-induction, are examined and shown to be unconvincing

After a brief presentation of what I take to be the representational démarche in science, I stress the fundamental role of true judgements in model construction. The success and correctness of a representation rests on the truth of judgements which attribute properties to real targeted entities, called “ontic judgements”. I then present what van Fraassen calls “the Loss of Reality objection”. After criticizing his dissolution of the objection, I offer an alternative way of answering the Loss of Reality objection by showing that the contact of our models with reality is grounded on the truth of ontic judgements. I conclude by examining.

A scientific mathematical law is causal if and only if it is a process law that contains a time derivative. This is the intrinsic criterion for causal laws we propose. A process is a space-time line along which some properties are conserved or vary. A process law contains a time variable, but only process laws that contain a time derivative are causal laws. An effect is identified with what corresponds to a time derivative of some property or magnitude in a process law, whereas the other terms correspond to the cause(s). According to our criterion, causes are simultaneous with their effects and causality has no temporal direction. Several examples from natural and social disciplines support the applicability of our criterion to all scientific laws. Various objections to our proposal are presented and refuted. The merits our intrinsic theory of causality vis-à-vis the Salmon–Dowe conserved quantity theory are discussed.

After a presentation of some relevant aspects of Chakravartty's semi-realism (A Metaphysics for scientific realism. Knowing the unobservable. Cambridge University Press, Cambridge, 2007), this paper addresses two difficulties that appear to be inherent to important components of his proposed metaphysics for scientific realism. First, if particulars and laws are concrete structures, namely actual groupings of causal properties as the semirealist contends, the relation between particulars and laws becomes also a relation between particulars with some annoying consequences. This worry—and some others—are resolved if laws are taken to be statements and particulars are construed not only as groupings of properties, but things that contain a non-conceptual ingredient which can be given in perceptual awareness. Second, on the semirealist's view of particulars it becomes difficult to defend an epistemological version of scientific realism according to which we have good reasons to believe that the same things are referred to despite the fact that successive theories may attribute different properties to them

This article argues that Thomas Kuhn's views on the existence of the world have undergone significant change in the course of his philosophical career. In Structure, Kuhn appears to be committed to the existence of the ordinary empirical world as well as the existence of an independent metaphysical world, but realism about the empirical world is abandoned in his later writings. Whereas in Structure the only relative worlds are the scientific worlds inhabited by the practitioners of various paradigms, the later Kuhn puts the non-scientific worlds of particular groups or cultures on the same footing as the paradigm-related scientific worlds. The article shows that, on what Ian Hacking called the "new-world problem", the later Kuhn has moved to a more radical antirealist position. It is also argued that the earlier and later solutions to the "new-world problem" face insuperable difficulties, which render Kuhn's account of scientific change implausible.