A note on the relationship between graphs and information protocols

Information protocols (IP’s) were developed to describe players who learn their social situation by their experiences. Although IP’s look similar to colored multi-graphs (MG’s), the two objects are constructed in fundamentally different ways. IP’s are constructed using the global concept of history, whereas graphs are constructed using the local concept of edges. We give necessary and sufficient conditions for each theory to be captured by the other. We find that the necessary and sufficient condition for IP theory to be captured by MG theory, which we call SE, excludes relevant game situations. Hence, we conclude that IP theory remains a vital tool and cannot be replaced by MG theory.     

Characterizing hallucination epistemically

According to the epistemic theory of hallucination, the fundamental psychological nature of a hallucinatory experience is constituted by its being ‘introspectively indiscriminable’, in some sense, from a veridical experience of a corresponding type. How is the notion of introspective indiscriminability to which the epistemic theory appeals best construed? Following M. G. F. Martin, the standard assumption is that the notion should be construed in terms of negative epistemics: in particular, it is assumed that the notion should be explained in terms of the impossibility that a hallucinator might possess a certain type of knowledge on a certain basis. I argue that the standard assumption is mistaken. I argue that the relevant notion of introspective indiscriminability is better construed in terms of positive epistemics: in particular, I argue that the notion is better explained by reference to the fact that it would be rational for a hallucinator positively to make a certain type of judgement, were that judgement made on a certain basis.     

Quantum logic as a dynamic logic

We address the old question whether a logical understanding of Quantum Mechanics requires abandoning some of the principles of classical logic. Against Putnam and others (Among whom we may count or not E. W. Beth, depending on how we interpret some of his statements), our answer is a clear “no”. Philosophically, our argument is based on combining a formal semantic approach, in the spirit of E. W. Beth’s proposal of applying Tarski’s semantical methods to the analysis of physical theories, with an empirical–experimental approach to Logic, as advocated by both Beth and Putnam, but understood by us in the view of the operational- realistic tradition of Jauch and Piron, i.e. as an investigation of “the logic of yes–no experiments” (or “questions”). Technically, we use the recently-developed setting of Quantum Dynamic Logic (Baltag and Smets 2005, 2008) to make explicit the operational meaning of quantum-mechanical concepts in our formal semantics. Based on our recent results (Baltag and Smets 2005), we show that the correct interpretation of quantum-logical connectives is dynamical, rather than purely propositional. We conclude that there is no contradiction between classical logic and (our dynamic reinterpretation of) quantum logic. Moreover, we argue that the Dynamic-Logical perspective leads to a better and deeper understanding of the “non-classicality” of quantum behavior than any perspective based on static Propositional Logic.     

Competitive equilibrium with intuitionistic agents

This paper studies an economy whose agents perceive their consumption possibilities subjectively, and whose preferences are defined on what they subjectively experience, rather than on those alternatives that are objectively present. The model of agents’ perceptions is based on intuitionistic logic. Roughly, this means that agents reason constructively: a solution to a problem exists only if there is a construction by which the problem can be solved. The theorems that can be proved determine how an agent perceives a set of alternatives. A dual model relates perceived alternatives to a shared language, which the agents use in trading. So perceptions relate objective alternatives to an agent’s subjective view of them, and reporting dually relates an agent’s subjective world to a shared language. It turns out that an appropriately modified notion of competitive equilibrium always exists. However, in contrast with standard results in economic theory, competitive equilibrium need not be efficient.     

Epistemic constraints on practical normativity

What is the relation between what we ought to do, on the one hand, and our epistemic access to the ought-giving facts, on the other? In assessing this, it is common to distinguish ‘objective’ from ‘subjective’ oughts. Very roughly, on the objectivist conception what an agent ought to do is determined by ought-giving facts in such a way that does not depend on the agent’s beliefs about, or epistemic access to, those facts; whereas on the subjectivist conception, what an agent ought to do depends on his beliefs. This paper defends the need for, and explicates, a third category of ‘ought’: ‘warranted oughts’. Section 1 introduces the distinction between objective and subjective ‘oughts’. Sections 2–3 draw attention to some serious problems with each. Section 4 examines, though rejects, a recent attempt to replace subjective ‘oughts’ with objective ‘wide-scope oughts’ operating on belief-action combinations. Section 5 explicates the notion of a warranted ‘ought’ and defends the account against some possible objections. The resulting a picture is one in which an adequate analysis of practical normativity requires both objective and warranted ‘oughts’. Section 6 concludes by responding to a worry about countenancing both.     

From data to phenomena: a Kantian stance

This paper investigates some metaphysical and epistemological assumptions behind Bogen and Woodward’s data-to-phenomena inferences. I raise a series of points and suggest an alternative possible Kantian stance about data-to-phenomena inferences. I clarify the nature of the suggested Kantian stance by contrasting it with McAllister’s view about phenomena as patterns in data sets.     

The scientistic stance: the empirical and materialist stances reconciled

van Fraassen (The empirical stance, 2002) contrasts the empirical stance with the materialist stance. The way he describes them makes both of them attractive, and while opposed they have something in common for both stances are scientific approaches to philosophy. The difference between them reflects their differing conceptions of science itself. Empiricists emphasise fallibilism, verifiability and falsifiability, and also to some extent scepticism and tolerance of novel hypotheses. Materialists regard the theoretical picture of the world as matter in motion as a true and explanatory account and insist on not taking ‘spooky’ entities or processes seriously as potential explanations of phenomena that so far lie outside the scope of successful science. The history of science shows us that both stances have been instrumental in the achievement of progress at various times. It is therefore plausible for a naturalist to suggest that science depends for its success on the dialectic between empiricism and materialism. A truly naturalist approach to philosophy ought then to synthesise them. Call the synthesized empiricist and materialist stances ‘the scientistic stance’. This paper elaborates and defends it.     

Reichenbach’s cubical universe and the problem of the external world

This paper is a sympathetic critique of the argument that Reichenbach develops in Chap. 2 of Experience and Prediction for the thesis that sense experience justifies belief in the existence of an external world. After discussing his attack on the positivist theory of meaning, I describe the probability ideas that Reichenbach presents. I argue that Reichenbach begins with an argument grounded in the Law of Likelihood but that he then endorses a different argument that involves prior probabilities. I try to show how this second step in Reichenbach’s approach can be strengthened by using ideas that have been developed recently for understanding causation in terms of the idea of intervention.