Peter Simons

Dans cet article, l’auteur présente la théorie bolzanienne du nombre. Il établit, sur la base d’une comparaison avec Frege, que la conception bolzanienne rencontre toutes les exigences d’une telle théorie tout en présentant plusieurs traits originaux, comme par exemple le fait qu’elle s’articule sur la base d’une théorie des « collections » , qui lui confèrent un intérêt philosophique certain. Tout en indiquant au passage un problème inhérent à la notion bolzanienne de Reihe, l’auteur présente la conception bolzanienne des nombres naturels, reconstruit sa théorie des nombres abstraits et montre comment Bolzano est en mesure d’établir le lien entre ces derniers et leur application aux ensembles concrets d’objets.In this article, the author exposes Bolzano’s theory of numbers. He shows, on the basis of a comparison with Frege, that Bolzano’s conception not only meets all the requisites of such a theory but also exhibits original features, such as for instance the fact that it is grounded in a theory of “collections” , which impart it with undeniable philosophical interest. After indicating one problem relating to the Bolzanian notion of a Reihe, the author presents Bolzano’s conception of natural numbers, reconstructs his theory of abstract numbers and expounds the connection between the latter and their application to concrete sets of things

Suppose you hold the following opinions in the philosophy of logic. First-order predicate logic is expressively inadequate to regiment concepts of mathematic and natural language; logicism is plausible and attractive; set theory as an adjunct to logic is unnatural and ontologically extravagant; humanly usable languages are finite in lexicon and syntax; it is worth striving for a Tarskian semantics for mathematics; there are no Platonic abstract objects. Then you are probably already in cognitive distress. One way to decease your unhappiness, short for embracing Platonism, is to accept higher-order logic and look, as did Arthur Prior, for a plausible way to neutralize the ontological commitment to abstract entities that this acceptance appears to entail.

Occurrents are entities that exist in time and, with few or no exceptions, extend over time as well, that is, they have parts corresponding to the different times at which they exist. This makes it very easy to say what makes it true that they exist at the times at which they do. Singular existential propositions, being contingent, positive and arguably atomic, stand in need of truth-makers, entities in virtue of whose existence they are true. The obvious candidate for what makes it true that Tony Blair exists is the Right Honourable Member for Sedgefield himself: by virtue of his existing, it is true that he exists. Nothing could be more straightforward. However, things that exist in time, with few exceptions, exist at some times and not at others. So a proposition to the effect that a certain object exists at a certain time likewise stands in need of a truth-maker, one matching the requirements of the existential proposition in question in its temporal specificity. Take an occurrent such as a boxing match and suppose it is going on twenty minutes after starting: by virtue of what is this true? The obvious answer here is that it is by virtue of the existence of that temporal part or phase which extends just over the time in question. Other temporal parts of the same occurrent which do not extend over this time do not act as truth-maker for the temporally specific existential proposition, this one does. There is no problem because occurrents do have temporal parts which can do this job.

The debate between 3- and 4-dimensionalists is one of the most lively and pervasive in current metaphysics. At stake is a glittering prize: the correct metaphysical analysis of material things and other objects commonly thought to persist in time by enduring. Since we count ourselves among such objects the outcome of the debate is of more than merely academic interest to us. Obviously the ramifications of the debate, even of the points raised by Kit Fine, go far beyond what I can discuss here, so I shall simply select some salient issues and comment on them from my own somewhat heterodox point of view.

From the beginning of the nineteenth century to the present day, philosophy in Austria has progressed through four phases. Theparticularities of the first three of these phases have prompted a number of commentators rightly to distinguish a characteristic Austrian, as distinct from German, way of doing philosophy. The main figure of the second phase was Franz Brentano, and his distinctive theory of the four-phase cycle of philosophical development is outlined, and critically compared to other views of the development of philosophy. In Austria itself the caesuras between the phases were marked as much by political as by philosophical events, and the paper shows how philosophy in Austria has been notable in all its phases for the high level and overwhelmingly negative effect of political interference in intellectual life, a doleful saga which continues to this day.

Commonsense ontology contains both continuants and occurrents, but are continuants necessary? I argue that they are neither occurrents nor easily replaceable by them. The worst problem for continuants is the question in virtue of what a given continuant exists at a given time. For such truthmakers we must have recourse to occurrents, those vital to the continuant at that time. Continuants are, like abstract objects, invariants under equivalences over occurrents. But they are not abstract, and their being invariants enables us to infer both their lack of temporal parts and that non-invariant predications about them must be relativized to times. \\\ [Joseph Melia] In this paper I try to eliminate occurrents from our ontology. I argue against Simons' position that occurrents are needed to supply truthmakers for existential claims about continuants. Nevertheless, those who would eliminate occurrents still need some account of our willingness to assert sentences that logically entail their existence. Though it turns out to be impossible to paraphrase away our reference to occurrents, I show that the truthmakers for such sentences are facts that involve only continuants. This is enough to allow us to regard our ordinary talk about occurrents as fictional. Finally, I argue that a proper conception of the underlying temporal facts about continuants can both avoid the problematic tensed theory of time and the problem of temporary intrinsics.