Online research in philosophy

Magical ersatzism is the view that possible worlds are primitive abstract entities. In On the Plurality of Worlds, David Lewis presented what appeared to many to be a devastating argument against magical ersatzism. In this paper, I show that Lewis’ central argument does not succeed. Magical ersatzism remains a viable theory of possible worlds.

This essay examines Kant's idea of organic teleology. The first two sections are devoted to Kant's analysis and justification of teleological conceptions in biology. Both the idea of teleology and Kant's anti-reductionism are derived from basic elements of his critical treatment of the human intellect. The third section discusses the limitations Kant places on accounts of origins in the life world. It is argued that the limitations Kant places on accounts of the origins of species do not follow from his idea of teleology. The final section briefly outlines the fate of the Kantian formulation of teleology in the nineteenth century.

The notion of a possible world is familiar from Leibniz’s philosophy, especially the idea – parodied by Voltaire in Candide – that the world we inhabit, the actual world, is the best of all possible worlds. But it was primarily in the latter half of the twentieth century that possible worlds became a mainstay of philosophical theorizing. In areas as diverse as philosophy of language, philosophy of science, epistemology, logic, ethics, and, of course, metaphysics itself, philosophers helped themselves to possible worlds in order to provide analyses of key concepts from their respective domains. David Lewis contributed analyses in all of these fields, most famously, perhaps, his possible worlds analysis of counterfactual conditionals (Lewis 1973). But these analyses invoking possible worlds cry out for a foundation: how is all this talk about possible worlds to be construed? Do possible worlds exist? If so, what is their nature?

Let’s fix some terminology at the start. A world (or possible world – for me, the ‘possible’ is redundant) is, first, an individual, not a set or class; second, a particular, not a property or universal; third, concrete in this sense: it is fully determinate in all qualitative respects; and, fourth, a maximal interrelated whole: each world is internally unified, and isolated from every other world.1 There is at least one world, the world we are part of. It is an actual world, the actual world if there are no “island universes.”2 Worlds that are not actual (if any) are merely possible. A realist about possible worlds believes that there is a plenitudinous plurality of worlds: whenever something is possible – for example, that donkeys talk, or that pigs fly – there is a world in which it is true.

Richard Sylvan died suddenly at the age of 60, when he had just completed this major text. But though this volume is the mature expression of one of our foremost modern philosophers, it remains, like all his work, pioneering, eclectic and controversial. Sylvan's theory of 'plurallism', the culmination of his life's work, is the subject of this important text. In his own characteristically provocative words, 'There is not merely a plurality of correct theories and more or less satisfactory worldviews: there is a corresponding plurality of actual worlds. Plurality penetrates deeper in full plurallism than linguistic surface or than conceptual or theoretical structure, to worlds...There is no single fact of the matter, there are facts and matters.'.

If a possible-worlds semantic theory for modal logics is pure, then the assertion of the theory, taken at face-value, can bring no commitment to the existence of a plurality of possible worlds (genuine or ersatz). But if we consider an applied theory (an application of the pure theory) in which the elements of the models are required to be possible worlds, then assertion of such a theory, taken at face-value, does appear to bring commitment to the existence of a plurality of possible worlds. Or at least that is so if the applied theory is adequate. For an applied possible-worlds semantic theory that is constrained to contain only one-world models is bound to deliver results on validity, soundness and completeness that are apt to seem disastrous. I attempt to steer a course between commitment to the existence of a plurality of possible worlds and commitment to such a disastrous applied possible-worlds semantics by noting, and developing, the position of one who asserts such a theory at face-value but who remains agnostic about the existence of other (non-actualized) possible worlds. Thus, a novel interpretation of applied possible-worlds semantics is offered on which we may lay claim to whatever benefits such a theory offers while avoiding realism about (other) possible worlds. Thereby, the contention that applied possible-worlds semantics gives us reason to be realists about possible worlds is (further) undermined.

This book is a defense of modal realism; the thesis that our world is but one of a plurality of worlds, and that the individuals that inhabit our world are only ...