Formal Philosophy

Logic at Columbia University

Leitgeb: The Humean Thesis on Belief

by Yang Liu

UNIVERSITY SEMINAR ON LOGIC, PROBABILITY, AND GAMES
The Humean Thesis on Belief
Hannes Leitgeb (Ludwig Maximilian University of Munich)
4:15 pm, May 2nd, 2014
716 Philosophy Hall, Columbia University

Abstract.  I am going to make precise, and assess, the following thesis on (all-or-nothing) belief and degrees of belief: It is rational to believe a proposition just in case it is rational to have a stably high degree of belief in it.I will start with some historical remarks, which are going to motivate calling this postulate the “Humean thesis on belief”. Once the thesis has been formulated in formal terms, it is possible to derive conclusions from it. Three of its consequences I will highlight in particular: doxastic logic; an instance of what is sometimes called the Lockean thesis on belief; and a simple qualitative decision theory.

Egan: Three Grades of Self-Involvement

by Ignacio Ojea

COLUMBIA PHILOSOPHY COLLOQUIUM
Three Grades of Self-Involvement
Andy Egan (Rutgers University)
4:10-6:00 PM, April 3rd, 2014
716 Philosophy Hall, Columbia University

Reception will follow

Ahmed: Causal Decision Theory and Intrapersonal Nash Equilibria

by Yang Liu

UNIVERSITY SEMINAR ON LOGIC, PROBABILITY, AND GAMES
Causal Decision Theory and Intrapersonal Nash Equilibria
Arif Ahmed (University of Cambridge)
4:15 PM, April 4th, 2014
716 Philosophy Hall, Columbia University

Abstract.  Most philosophers today prefer ‘Causal Decision Theory’ to Bayesian or other non-Causal Decision Theories. What explains this is the fact that in certain Newcomb-like cases, only Causal theories recommend an option on which you would have done better, whatever the state of the world had been. But if so, there are cases of sequential choice in which the same difficulty arises for Causal Decision Theory. Worse: under further light assumptions the Causal Theory faces a money pump in these cases. It may be illuminating to consider rational sequential choice as an intrapersonal game between one’s stages, and if time permits I will do this. In that light the difficulty for Causal Decision Theory appears to be that it allows, but its non-causal rivals do not allow, for Nash equilibria in such games that are Pareto inefficient.

Ojea: Evaluation Games for Many Valued Logics

by Ignacio Ojea

CUNY SEMINAR IN LOGIC, PROBABILITY, AND GAMES
Evaluation Games for many valued logics
Ignacio Ojea (Columbia University)
4:15 PM, March 28th, 2014
Room 3305, CUNY Graduate Center

Abstract.  Evaluation Games for classical logic are well known. Following early applications of games in model theory, by Ehrenfeucht and Fraisse, Hintikka and Parikh independently proposed a game-theoretic approach as a way of defining the classical semantics. A great deal of the game theoretic approach has been more recently studied by van Bentham. The original idea was to define the truth-value of a wff, in a given model, in terms of the existence of a strategy for one of the players (the “Verifier” and “Falsifier”) in a certain two-person game. These games can be also viewed in terms of pay-offs. Recently I suggested a natural extension of these games to the case of many valued logics, where the notion of a Nash equilibrium plays a crucial role.

Georgatos: Topologic – old and new results

by Yang Liu

CUNY SEMINAR IN LOGIC, PROBABILITY, AND GAMES
Topologic: old and new results
Konstantinos Georgatos (CUNY)
4:15 PM, Friday, March 21, 2014
Room 3305, CUNY GC

Abstract. In 1992, Moss and Parikh introduced Toplogic an epistemic modal logic whose semanticas are based on subsets. Since then, research on this logic and it many extensions has been going strong. I will survey most of these results in the first part of this talk. On the second part, I will present how topologic can form a basis for the formalization of belief change operators, such as update, conditionals and contraction. Arbitrary nestings and iterations of such operators are easily automatized which is not the case in other studies of belief change in object language.

Ijjas: Cosmology at the Crossroads

by Yang Liu

NY/NJ PHILOSOPHY OF SCIENCE GROUP
Cosmology at the Crossroads
Anna Ijjas (Princeton)
4:10 – 6:00pm PM , March 3, 2014
201D Philosophy Hall, Columbia University

Abstract. Thirty years of inflation have greatly changed modern cosmological thinking. Most importantly, inflation provides a paradigm for the generation of primordial density fluctuations seeding the structure of our universe, by stretching quantum fluctuations to cosmological distances. However, the physics governing the evolution of the very early universe before nucleosynthesis remains a challenge for modern theoretical cosmology. In this talk, I will begin by reviewing inflationary cosmology and discussing the reasons why most cosmologists today consider it to be the leading paradigm. Then, I will turn to the flaws of inflationary thinking and present possible ways out.