In this paper two theories of defeasible reasoning, Pollock's account and my theory of ranking functions, are compared, on a strategic level, since a strictly formal comparison would have been unfeasible. A brief summary of the accounts shows their basic difference: Pollock's is a strictly computational one, whereas ranking functions provide a regulative theory. Consequently, I argue that Pollock's theory is normatively defective, unable to provide a theoretical justification for its basic inference rules and thus an independent notion of admissible (...) rules. Conversely, I explain how quite a number of achievements of Pollock's account can be adequately duplicated within ranking theory. The main purpose of the paper, though, is not to settle a dispute with formal epistemology, but rather to emphasize the importance of formal methods to the whole of epistemology. (shrink)

The theory of concepts advanced in the dissertation aims at accounting for a) how a concept makes successful practice possible, and b) how a scientific concept can be subject to rational change in the course of history. Traditional accounts in the philosophy of science have usually studied concepts in terms only of their reference; their concern is to establish a stability of reference in order to address the incommensurability problem. My discussion, in contrast, suggests that each scientific concept consists of (...) three components of content: 1) reference, 2) inferential role, and 3) the epistemic goal pursued with the concept's use. I argue that in the course of history a concept can change in any of these three components, and that change in one component—including change of reference—can be accounted for as being rational relative to other components, in particular a concept's epistemic goal.This semantic framework is applied to two cases from the history of biology: the homology concept as used in 19th and 20th century biology, and the gene concept as used in different parts of the 20th century. The homology case study argues that the advent of Darwinian evolutionary theory, despite introducing a new definition of homology, did not bring about a new homology concept (distinct from the pre-Darwinian concept) in the 19th century. Nowadays, however, distinct homology concepts are used in systematics/evolutionary biology, in evolutionary developmental biology, and in molecular biology. The emergence of these different homology concepts is explained as occurring in a rational fashion. The gene case study argues that conceptual progress occurred with the transition from the classical to the molecular gene concept, despite a change in reference. In the last two decades, change occurred internal to the molecular gene concept, so that nowadays this concept's usage and reference varies from context to context. I argue that this situation emerged rationally and that the current variation in usage and reference is conducive to biological practice.The dissertation uses ideas and methodological tools from the philosophy of mind and language, the philosophy of science, the history of science, and the psychology of concepts. (shrink)

David Chalmers and Frank Jackson have promoted a strong program of conceptual analysis, which accords a significant philosophical role to the a priori analysis of concepts. They found this methodological program on an account of concepts using two-dimensional semantics. This paper argues that Chalmers and Jackson’s account of concepts, and the related approach by David Braddon-Mitchell, is inadequate for natural kind concepts as found in biology. Two-dimensional semantics is metaphysically faulty as an account of the nature of concepts and concept (...) possession. It is also methodologically flawed as a guideline for how to study scientific concepts. Proponents of two-dimensional semantics are criticized for not taking seriously semantic variation between persons and for failing to adequately account for the rationality of semantic change. I suggest a more pragmatic approach to natural kind term meaning, arguing that the epistemic goal pursued by a term’s use is an additional semantic property. (shrink)

The paper argues that the objects of belief should not be conceived as sets of possible worlds or propositions of set of centered possible worlds or egocentric propositions (this is the propositional conception), but rather as sets of pairs consisting of a centered world and a sequence of objects (this is the intentional conception of the objects of belief). The paper explains the deep significance of this thesis for the framework of two-dimensional semantics, indeed for any framework trying to adequately (...) relate semantics and epistemology (which is here construed as what I call the Congruence Principle). I give three arguments for this thesis, two preliminary indecisive ones by way of examples, and third theoretical one alluding to a deep principle of philosophical psychology (which I call the Invariance Principle). This paper is an improved and up-dated version of my paper No. 25. It will appear in Causation, Coherence, and Concepts. A Collection of Essays of mine. (shrink)

"Five Questions on Formal Philosophy": Like the other authors in the volume, I was asked for my reflections on the character of philosophy by answering the following five questions : 1. Why were you initially drawn to formal methods? 2. What example from your work illustrates the role formal methods can play in philosophy? 3. What is the proper role of philosophy in relation to other disciplines? 4. What do you consider the most neglected topics and/or contributions in late 20th (...) century philosophy? 5. What are the most important problems in philosophy and which are the prospects for progress? (shrink)

The paper identifies two major strands of truth theories, ontological and epistemological ones, and argues that both are of equal primacy and find their home within two-dimensional semantics. Contrary to received views, it argues further that epistemological truth theories operate on Lewisian possible worlds and ontological truth theories on Wittgensteinian possible worlds and that both are mediated by the so-called epistemic-ontic map the further specification of which is of utmost philosophical importance.

The paper discusses concept individuation in the context of scientific concepts and conceptual change in science. It is argued that some concepts can be individuated in different ways. A particular term may be viewed as corresponding to a single concept. But at the same time, we can legitimately individuate in a more fine grained manner, i.e., this term can also be considered as corresponding to two or several concepts. The reason is that there are different philosophical and explanatory interests that (...) underlie a particular study of the change of a scientific term. These interests determine how a concept is to be individuated; and as the same term can be subject to different philosophical studies and interests, its content can be individuated in different ways. (shrink)