Ojea: Evaluation Games for Many Valued Logics

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

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

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.

Stalnaker: Modeling Credibility

Modeling Credibility
Robert Stalnaker (MIT/Columbia)
4:15 – 6:15 PM, Friday, December 6, 2013
Room 6496, CUNY GC

Abstract. A “cheap talk” move in a game is a move that does not affect either the subsequent moves available, or the payoffs, for any of the players. The point of such a move can only be to convey information to the other players, but nothing endogenous to the game can determine either what information the player aims to convey, or whether she will be successful in conveying that information. We might add to the game a language that is presumed to be common knowledge among the players, with a semantics that determines the informational content of the cheap talk moves. But since these moves do not affect any payoffs, there is no assurance that the players will tell the truth. My concern in this talk will be with the problem of characterizing the conditions under which a cheap talk message will be credible: the conditions under which players receiving a message will have reason to believe that the sending player is telling the truth. The rough idea is that a message is credible when the payoffs are such that the sending player wants the receiving player to believe the message only if it is true, but there are problems making this idea precise. I will look at some simple and familiar games when they are preceded by a cheap talk move in which a player has the opportunity to signal what moves he intends to make, and at some signaling games that raise problems for the definition of credibility.

Parikh: Justified True Belief

Justified True Belief: Plato, Gettier and Turing
Rohit Parikh (CUNY)
September 24, 2013, 2:00 PM,
Room 3209, CUNY GC
Abstract. We examine the relationship between the justified true belief (JTB) account of knowledge and Plato’s theory about it as expounded in the Theaetetus. Considering Socrates’ remarks in the Theaetetus brings us to some concerns raised by Turing and to Wittgenstein’s famous comment explanations come to an end somewhere. We present two simple technical results which bear on the question. And finally, we look at the pragmatic aspects of knowledge attributions.

Parikh: Epistemic logic, games and social software

Epistemic Logic, Games and Social Software: some old and new ideas
Rohit Parikh (CUNY)
September 19, 2013, 4:15 PM,
Room 9204/9205, CUNY GC
Abstract. epistemic reasoning has gradually matured from being the domain of philosophers and logicians to becoming relevant also in economics and social science. But theoretical computer science and game theory remain as two of the most powerful tools which epistemologists can wield. Epistemic tools have been used by writers as different from each other as Shakespeare, Shaw and O’Henry. Even the Indian epic Mahabharata contains stories whose main point is epistemic. But more recently there has been technical work devoted to what might be called applied epistemic logic, and CUNY has been one of the leaders. CUNY collaborators include Walter Dean, Cagil Tasdemir and Andreas Witzel. Eric Pacuit, who got his doctorate from CUNY some years ago, has now become a household word in epistemic circles. And Artemov’s own interest in Game theory has a very strong epistemic flavor. There are also very important questions about the extent to which epistemic considerations enter into animal behavior. Major figures like Peter Godfrey-Smith and Robert Lurz at CUNY have contributed to this field which began with some questions raised by Premack and Woodruff at U. Penn. We cannot possibly do justice to all this work in a single talk but will try to give a bird’s eye view and indicate one or two “cute” results.