Formal Philosophy

Logic at Columbia University

Parikh: Formalizing the Umwelt

by Robby

Formalizing the Umwelt
Rohit Parikh (CUNY)
4:10 pm, Friday, Dec. 1st, 2017
Faculty House, Columbia University

Abstract. The umwelt is a notion invented by the Baltic-German biologist Jakob von Uexküll.  It represents how a creature, an animal, a child or even an adult “sees” the world and is a precursor to the Wumpus world in contemporary AI literature.  A fly is caught in a spider’s web because its vision is too coarse to see the fine threads of the web.  Thus though the web is part of the world, it is not a part of the fly’s umwelt.   Similarly a tick will suck not only on blood but also on any warm liquid covered by a membrane.  In the tick’s umwelt, the blood and the warm liquid are “the same”.

We represent an umwelt as a homomorphic image of the real world in which the creature, whatever it might be, has some perceptions, some powers, and some preferences (utilities for convenience).  Thus we can calculate the average utility of an umwelt and also the utilities of two creatures combining their umwelts into a symbiosis.

A creature may also have a “theory” which is a map from sets of atomic sentences to sets of atomic sentences.   Atomic sentences which are observed may allow the creature to infer other atomic sentences not observed.  This weak but useful notion of theory bypasses some of Davidson’s objections to animals having beliefs.

Russell, Stuart J., and Peter Norvig. “Artificial intelligence: a modern approach (International Edition).” (2002).

Von Uexküll, J., von Uexküll, M., & O’Neil, J. D. (2010). A foray into the worlds of animals and humans: With a theory of meaning. U of Minnesota Press.​


Synthese S.I. on Decision Theory and the Future of Artificial Intelligence

by Yang Liu

Guest Editors:
Stephan Hartmann (LMU Munich)
Yang Liu (University of Cambridge)
Huw Price (University of Cambridge)

There is increasing interest in the challenges of ensuring that the long-term development of artificial intelligence (AI) is safe and beneficial. Moreover, despite different perspectives, there is much common ground between mathematical and philosophical decision theory, on the one hand, and AI, on the other. The aim of the special issue is to explore links and joint research at the nexus between decision theory and AI, broadly construed.

We welcome submissions of individual papers covering topics in philosophy, artificial intelligence and cognitive science that involve decision making including, but not limited to, subjects on

  • causality
  • decision making with bounded resources
  • foundations of probability theory
  • philosophy of machine learning
  • philosophical and mathematical decision/game theory

Contributions must be original and not under review elsewhere. Although there is no prescribed word or page limit for submissions to Synthese, as a rule of thumb, papers typically tend to be between 15 and 30 printed pages (in the journal’s printed format). Submissions should also include a separate title page containing the contact details of the author(s), an abstract (150-250 words) and a list of 4-6 keywords. All papers will be subject to the journal’s standard double-blind peer-review.

Manuscripts should be submitted online through Editorial Manager: Please choose the appropriate article type for your submission by selecting “S.I. : DecTheory&FutOfAI” from the relevant drop down menu.

The deadline for submissions is February 15, 2018.
For further information about the special issue, please visit the website:

Vasudevan: Entropy and Insufficient Reason

by Robby

Entropy and Insufficient Reason
Anubav Vasudevan (University of Chicago)
4:10 pm, Friday, November 10th, 2017
Faculty House, Columbia University

Abstract. One well-known objection to the principle of maximum entropy is the so-called Judy Benjamin problem, first introduced by van Fraassen (1981). The problem turns on the apparently puzzling fact that, on the basis of information relating an event’s conditional probability, the maximum entropy distribution will almost always assign to the event conditionalized on a probability strictly less than that assigned to it by the uniform distribution. In this paper, I present an analysis of the Judy Benjamin problem that can help to make sense of this seemingly odd feature of maximum entropy inference. My analysis is based on the claim that, in applying the principle of maximum entropy, Judy Benjamin is not acting out of a concern to maximize uncertainty in the face of new evidence, but is rather exercising a certain brand of epistemic charity towards her informant. This charity takes the form of an assumption on the part of Judy Benjamin that her informant’s evidential report leaves out no relevant information. I will explain how this single assumption suffices to rationalize Judy Benjamin’s behavior. I will then explain how such a re-conceptualization of the motives underlying Judy Benjamin’s appeal to the principle of maximum entropy can further our understanding of the relationship between this principle and the principle of insufficient reason. I will conclude with a discussion of the foundational significance for probability theory of ergodic theorems (e.g., de Finetti’s theorem) describing the asymptotic behavior of measure preserving transformation groups. In particular, I will explain how these results, which serve as the basis of maximum entropy inference, can provide a unified conceptual framework in which to justify both a priori and a posteriori probabilistic reasoning.

Button: Internal categoricity and internal realism in the philosophy of mathematics

by Robby

Internal categoricity and internal realism in the philosophy of mathematics

Tim Button (University of Cambridge)
4:10 pm, Wednesday, April 19th, 2017
Faculty House, Columbia University

Abstract. Many philosophers think that mathematics is about ‘structure’. Many philosophers would also explicate this notion of ‘structure’ via model theory. But the Compactness and Löwenheim–Skolem theorems lead to some famously hard questions for this view. They threaten to leave us unable to talk about any particular ‘structure’.

In this talk, I outline how we might explicate ‘structure’ without appealing to model theory, and indeed without invoking any kind of semantic ascent. The approach involves making use of internal categoricity. I will outline the idea of internal categoricity, state some results, and use these results to make sense of Putnam’s beautiful but cryptic claim: “Models are not lost noumenal waifs looking for someone to name them; they are constructions within our theory itself, and they have names from birth.”

Columbia Festival of Formal Philosophy

by Yang Liu

A series of logic related talks at Columbia University in the next a few weeks. Please click the link of each talk series below for more information.

by Kenny Easwaran (Texas A&M University)

Graduate Workshop
Measuring Beliefs
3:00 pm – 5:00 pm, Friday, March 31, 2017
716 Philosophy Hall, Columbia University

Departmental Lecture
An Opinionated Introduction to the Foundations of Bayesianism
4:10 pm – 6:00 pm, Tuesday, April 4, 2017
716 Philosophy Hall, Columbia University
Reception to follow in 720 Philosophy Hall

Public Lecture
Unity in Diversity: “The City as a Collective Agent”
4:10 pm – 6:00 pm, Thursday, April 6, 2017
603 Hamilton Hall, Columbia University

Gödel’s Disjunction
Peter Koellner (Harvard University)
5:00 pm, Friday, April 7th, 2017
716 Philosophy Hall, Columbia University
Dinner to follow at Faculty House

Saturday, April 8th, 2017
716 Philosophy Hall, Columbia University

10:00 am – 11:30 am
Gordon Belot (University of Michigan)

11:45 am – 13:15 pm
Schnorr Randomness and Lévi’s Martingale Convergence Theorem
Simon Huttegger (UC Irvine)

2:45 pm – 4:15 pm
Probing With Severity: Beyond Bayesian Probabilism and Frequentist Performance
Deborah Mayo (Virginia Tech)

4:30 pm – 6:00 pm
Radically Elementary Imprecise Probability Based on Extensive Measurement
Teddy Seidenfeld (Carnegie Mellon University)
Reception to follow

Koellner: Gödel’s Disjunction

by Robby

Gödel’s Disjunction
Peter Koellner (Harvard University)
5:00 pm, Friday, April 7th, 2017
716 Philosophy Hall, Columbia University

Abstract. Gödel’s disjunction asserts that either “the mind cannot be mechanized” or “there are absolutely undecidable statements.” Arguments are examined for and against each disjunct in the context of precise frameworks governing the notions of absolute provability and truth. The focus is on Penrose’s new argument, which interestingly involves type-free truth. In order to reconstruct Penrose’s argument, a system, DKT, is devised for absolute provability and type-free truth. It turns out that in this setting there are actually two versions of the disjunction and its disjuncts. The first, fully general versions end up being (provably) indeterminate. The second, restricted versions end up being (provably) determinate, and so, in this case there is at least an initial prospect of success. However, in this case it will be seen that although the disjunction itself is provable, neither disjunct is provable nor refutable in the framework.