En ce XXe siècle, où la physique s'est identifiée à la science révolutionnaire par excellence, l'œuvre passionnée d'Ilya Prigogine constitue une singulière anomalie. Anormale parce qu'elle prend le parti du monde des phénomènes physiques contre le pouvoir de la théorie, jugé abusif ; mais anormale aussi par sa longue obstination à une époque où la rapidité fait foi. Le combat avait commencé au début des années soixante, sur un mode mineur : Prigogine demandait à ses collègues de reconnaître qu' " (...) il y a certainement une signification physique profonde dans l'équation de Boltzman ". Thèse apparemment bien légitime : l'équation de Boltzmann permet de décrire avec succès le comportement de non-équilibre des gaz dilués. Mais thèse iconoclaste : car, depuis que la croissance de l'entropie a été renvoyée aux seules probabilités, le comportement de non-équilibre n'est plus sensé autoriser la moindre " signification profonde ". Raconter l'histoire de ce combat, comme le fait Isabelle Stengers dans ce livre, revient à interroger les lois fondamentales sous l'angle du lien entre théorie, valeur et obligation. En effet, sans ce lien, ni la position de Prigogine ni celle des physiciens contre qui il va chercher des arguments toujours plus puissants ne sont intelligibles. L'auteur montre que ce lien permet d' " inventer " des problèmes : Il y a Prigogine qui oppose ainsi des lois nouvelles, les " lois du chaos ", au déterminisme absolu des lois fondamentales de la physique. La physique est habitée par la passion de la loi, mais la manière dont cette passion est ici réinventée pourrait ouvrir de nouvelles voies, vitales pour une " écologie des pratiques ". Serait-il possible que le physicien ne se présente plus comme celui par qui s'opère la fascinante découverte des lois de la nature? Serait-il possible de célébrer avec lui l'extraordinaire aventure que constitue l'invention d'un objet capable de dicter la manière dont il doit être décrit? (shrink)

Perhaps if the future existed, concretely and individually, as something that could be discerned by a better brain, the past would not be so seductive: its demands would he balanced by those of the future. Persons might then straddle the middle stretch of the seesaw when considering this or that object. It might be fun. But the future has no such reality (as the pictured past and the perceived present possess); the future is but a figure of speech, a specter (...) of thought. (shrink)

The species of indeterminist tense logic called Peircean by A. N. Prior is proved to be recursively decidable.

The formal time symmetry of the quantum measurement process is extensively discussed. Then, the origin of the alleged association between a fixed temporal direction and quantum measurements is investigated. It is shown that some features of such an association might arise from epistemological rather than purely physical assumptions. In particular, it is brought out that a sequence of statements bearing on quantum measurements may display intrinsic asymmetric properties, irrespective of the location of corresponding measurements in time t of the Schrodinger (...) equation. The situation of an observer performing two measurements in two opposite directions of t is eventually investigated. Essential differences are found between two descriptions of this situation: the internal one (taking only into account what is recorded in the observer's memory) and the external one (whereby the observer is considered as a quantum system ruled by the Schrodinger equation). Finally, a method allowing several observers to establish a correspondence between their memory sizes is analyzed. The most important facts that usually lead to the associating of a preferential temporal direction with quantum measurements may be inferred from this correspondence. (shrink)

by Sir Karl Popper This is a great book, and an exciting book. I say so even though I happen to dis agree with the author in many minor points and one or two major points. Some of the minor points are merely terminological, and therefore very minor. I dislike the term 'dialectic', because of its use since Hegel and Marx; and I dislike the term 'gravitism', perhaps without a good reason. Thus I dislike the name which Professor Gal-Or has (...) given to his theory. But the theory seems to me a great and a very beauti ful theory, so far as I can judge. Other minor points of disagreement are connected with Gal-Or's original and remarkable views of the great philosophers, including Spinoza and Kant. A major point of disagreement is that Gal-Or, following Einstein, is a scientific determinist, while I cannot but regard determinism as a modem super stition. Of course, he may be right and I may be completely mistaken. I mention these critical points rather in order to emphasize how strongly I am impressed by Professor Gal-Or's great book. Even in the very unlikely case that, wherever we disagree, he should be in the wrong and I right, even if that should be the case (which is improbable in the extreme), it would remain a great book: readable, worth reading and enlightening; with a most fascinating cosmological story of time, expansion, and gravitation. (shrink)