Believing as Deciding
André Fuhrmann, Erik Olsson, Hans Rott
This project is about the relation between practical and theoretical reason. In our view, it is not plausible to assume that the values that enter into these two different domains are of the same sort. Rather, theoretical inquiry is driven by special theoretical values (probability, information content, simplicity and so on) and not by considerations of practical utility. Nevertheless, our central conjecture is that there may still be a structural parallel between practical deliberation and theoretical inquiry. This structural unity thesis which has previously been advocated by philosophers in the American pragmatist tradition, most importantly by Isaac Levi, was revived recently through Hans Rott’s disclosure of a far-reaching formal similarity between, on the one hand, the theory of rational choice and, on the other hand, certain theories of belief revision (AGM) and non-monotonic reasoning. Rott’s results can be found in his book Change, Choice and Inference with Oxford University Press. In the first phase of this project, the most important aim was to assess the philosophical force of these formal results. This was done in Olsson’s paper “Belief Revision, Rational Choice and the Unity of Reason” (to appear in Studia Logica in a special issue on belief revision edited by Olsson).
In the second phase of the project, we have sought to obtain a more thorough understanding of the belief revision process by widening the perspective to include (1) the driving forces behind belief changes and (2) a more detailed account of the mechanisms whereby a new proposition is accepted as a belief. Olsson has addressed the driving forces from a Peircean perspective in his “Pragmatismus und Skeptizismus” (to appear in Pragmatismus heute, a collection of papers on pragmatism edited by Fuhrmann and Olsson). He has studied the process of observation in decision theoretic terms in his paper “Avoiding Epistemic Hell: Levi on Observation and Inconsistency” (to appear in Synthese) where he criticizes Levi’s construal of observation as routine expansion. This criticism has prompted Levi to make important changes in his theory, as described in Levi’s forthcoming reply to Olsson in Synthese.
The central role in this project played by the concept of coherence ensures a close connection to the project of Spohn, Halbach et al. Among Olsson’s many contributions to this topic we would like to mention his “What is the Problem of Coherence and Truth?” in The Journal of Philosophy (2002) and “Coherence, Reliability and Bayesian Networks” (with Luc Bovens) in Mind (2000). The related issue of witness corroboration is studied in his “Corroborating Testimony, Probability and Surprise” in The British Journal for the Philosophy of Science (2002). Moreover, Olsson is the editor of a forthcoming book with Kluwer on the coherence theory of Keith Lehrer (The Epistemology of Keith Lehrer) to which Halbach, Rott and Spohn have also contributed.
Coherence Theories of Knowledge
Ludwig Fahrbach, Christoph Fehige, Volker Halbach, Wolfgang Spohn
When beliefs are justified, what is the structure of their justification? According to foundationalism, all justification rests in the end on basic beliefs that do not require further justification; they are supposed to be “self-justifiying”. All other justified beliefs inherit their status from those basic beliefs. However, the beliefs that we might be prepared to treat as self-justifying are unlikely to form sufficient foundations for our knowledge. Foundationalism – at least in its stronger forms – seems to adhere to the myth of the given, and the attacks on this myth from various sides have been successful. Thus foundationalism does not provide a correct account of the structure of justification.
Coherentism is understood as the array of non-foundationalist approaches to the theory of justification. According to coherentism, a belief is justfied if it “coheres” with a system of beliefs. Several coherentist accounts of the justification of empirical beliefs have been put forward and studied by epistemologists. Coherentism faces several challenges. It needs to provide a picture of how empirical input is possible at all. Moreover, some accounts of coherence put epistemic justification out of reach by putting coherence itself out of reach – coherence, on these accounts, cannot be grasped by beings with our computational abilities. We intend to show, however, that the restriction imposed by metamathematical results are less severe than some epistemologists have claimed.
Among philosophers of mathematics, “antifoundationalism” has recently received considerable attention. Although mathematics has provided the model for foundationalism, mathematical justification itself seems to be locally foundationalist at best. The basic “beliefs” in mathematics, the mathematical axioms, are no more self-justifying than ordinary empirical beliefs. The results in Reverse Mathematics suggest the picture of a web of mathematical beliefs that support each other. Axioms turn out to be equivalent to other mathematical principles and theorems, and the “axiom” inherits its plausibility from (at least some of) its consequences just as much as the consequences inherit their epistemic status from the allegedly self-justifying axiom. In this project, we are especially interested in a holistic approach. We seek a uniform notion of justification that will suit both empirical and mathematical beliefs. We combine recent anti-foundationalist approaches from two areas: epistemology and the philosophy of science. In particular, we explore the relation of anti-foundationalist structuralism in philosophy of mathematics, as put forward by Stewart Shapiro and others, with coherentism in epistemology.
Cognitive and Referential Aspects of Concepts
Ulrike Haas-Spohn, Hans Kamp
In its first part the project dealt with the logical form of ascriptions of propositional attitudes, in particular of beliefs. It turned out that existing theories both of doxastic states themselves and of their contents were in an unsatisfactory condition. What is missing is a good theory of concepts that obeys various constraints, including the following:
- that concepts refer to objects (usually external ones);
- that concepts are within the cognitive grasp or the subjective competence of the language user (in contrast to meanings if those “ain’t in the head”);
- that concepts compositionally generate the contents of belief.
The recent literature shows that the interest in such a theory is immense. The project attempts to advance its own theory of concepts. In doing so, it compares and discusses the literature; hooks up with thoughts on conceptual change as discussed lately in the philosophy of science; and builds a bridge to approaches in linguistics and cognitive science.
The Semantic Conception of the A Priori
Hans Kamp, Manfred Kupffer, Wolfgang Spohn
Some things that we know we know a priori—that is, independently of any experience. We know, for example, that if p, then p; that everything is as it actually is; and that no totally green surface can be totally red at the same time. Note that we know all these things without having bothered to verify them. Indeed, for such things no possible experience could tell us that what we thought we knew was really false.
According to the semantic conception of the a priori, apriority derives from meaning. Sometimes apriority is even defined in purely semantic terms. For instance, the logical positivists held that apriority and analyticity (truth solely in virtue of meaning) are one and the same. Even though in his groundbreaking essay “Naming and Necessity” Saul Kripke has shown these two notions to differ, later attempts to build on Kripke’s work have continued to yield purely semantic definitions of the a priori. According to David Kaplan, for example, a sentence is a priori if and only if it expresses, in every context of utterance, some proposition that is true in that context.
Such a semantic redefinition of an epistemological notion like knowledge (or knowability) a priori might look beside the point. The present project, however, intends to justify Kaplan's characterisation of the a priori by deriving it from epistemic premises; to generalise it and thus make it suitable for additional applications; and to compare it to other existing conceptions of the a priori. Technically, all this is placed in the framework of two-dimensional modal logic, a framework that has lately received a great amount of attention as a tool in the philosophy of mind, especially in the debate about consciousness. We hope to contribute to a better philosophical understanding of that framework.
Exemplary Writings: Kaplan’s A priori
A Structural Theory of Properties
Ulf Friedrichsdorf, Holger Sturm
The main task of this project is to develop a general theory of properties and codify it into a suitable formal framework. The theory should meet the following two demands: First, it should cover our basic intuitions concerning the nature of properties, and, second, it should provide a precise and detailed description of the realm of properties, so that it can be used for foundational purposes within different areas of philosophy, like natural ontology and philosophy of mind. The project is inspired by the idea that the realm of properties can only be characterized—and demarcated from other ontological domains—in a proper way by means of its internal structure. This structure is determined by a number of parameters the most important of which are: a taxonomy of the different kinds of properties, the relationship between simple and complex properties, identitiy conditions, and the interplay between properties and modalities.
The project is carried out in four steps. In the first step, we deal with some methodological aspects. In particular, we evaluate the standard arguments that were given in favor of the existence of properties, and try to clarify in what sense properties can help to explain phenomena of philosophical interest. In the second step, we design a kind of minimal or basic theory of properties, and describe it formally in the shape of an axiomatic system. The purpose of the third step is to enrich the basic theory by some of the above mentioned aspects that structure the realm of properties. At present, we are mainly concentrating on the analysis of some important kinds of properties—especially, intrinsic and natural properties. As for the logical point of view, we are interested in finding out to what extent these aspects can be covered within an axiomatic theory. In the final step, we work on applications of our theory within the philosophy of mind. The centre of our attention is the analysis of different notions of reduction and supervenience.