Mario Gomez-Torrente

Taking as premises some reasonable principles about the essences of natural numbers, pluralities and sets, the paper offers two types of argument for the conclusions that the natural numbers could not be the Zermelo numbers, the von Neumann numbers, the “Kripke numbers”, or the positions in the ω-structure, among other things. These conclusions are thus Benacerrafian in form, but it is emphasized that the two kinds of argument offered in the paper are anti-Benacerrafian in substance, as they are perfectly compatible and in fact congenial with some views on which the numbers could be things of certain other kinds.

Among the influential contributions of Alfred Tarski to logic and philosophy, and close in importance to his widely applied and discussed definition of truth, one finds his definition of logical consequence for formal languages. Like his definition of truth, Tarski's definition of logical consequence has been widely and fruitfully applied. Unlike the definition of truth, that of logical consequence has been rarely discussed philosophically. The main aim of this dissertation is to offer a thorough discussion of some philosophical issues arising from the neglected definition. ;The point of departure is an interpretative reading of the relevant writings by Tarski. This reading yields historically interesting data that refute other recent readings. It also provides philosophical illumination, by clarifying how Tarski thought that his definition satisfied some pretheoretic desiderata. ;Next it is discussed whether Tarski's definition satisfies other pretheoretic desiderata, not stated by Tarski and in some cases not endorsed by him, but which are desiderata nonetheless from reasonable standpoints. These include the desiderata that all instances of logical consequence in Tarski's defined sense be instances of analytical implication, and that they be instances of valid implication. The conclusion of this part of the dissertation is that, under reasonable assumptions regarding the field of applicability of the definition and the concepts used in it, there are reasons to believe that these desiderata are met, and none to believe they are not. ;Finally, the problem of logical constants is examined. The concept of a "logical constant" is the only concept not taken from logic and mathematics that appears in Tarski's definition. The problem of logical constants is that of replacing the primitive 'logical constant' with a defined, better understood concept, and in a such a way that the resulting defined concept of logical consequence meets the previously discussed desiderata. The main conclusion of this part is that some attempts to do this replace the obscure with the more obscure, while other attempts that seem to be in the right spirit have shortcomings of their own

I argue that recent defenses of the view that in 1936 Tarski required all interpretations of a language to share one same domain of quantification are based on misinterpretations of Tarski’s texts. In particular, I rebut some criticisms of my earlier attack on the fixed-domain exegesis and I offer a more detailed report of the textual evidence on the issue than in my earlier work. I also offer new considerations on subsisting issues of interpretation concerning Tarski’s views on the logical correctness of certain omega-arguments, on the Tarskian proof that Etchemendy took to be modal and fallacious, and on Tarski’s appeals to the “common concept of consequence”.

The pretheoretical notions of logical consequence and of a logical expression are linked in vague and complex ways to modal and pragmatic intuitions. I offer an introduction to the difficulties that these intuitions create when one attempts to give precise characterizations of those notions. Special attention is given to Tarski’s theories of logical consequence and logical constancy. I note that the Tarskian theory of logical consequence has fared better in the face of the difficulties than the Tarskian theory of logical constancy. Other theories of these notions are explained and criticized.