Philip Sink

Philip Sink

he/him

PhD Student in Logic, Computation, and Methodology in the Philosophy Department at Carnegie Mellon University.
My main area of study is Modal Logic, with a focus on Simplicial Semantics and applications to Distributed Computing.

Posts by Collection

portfolio

publications

Modal Logic Without Possible Worlds: A New Semantics for Modal Logic in Simplicial Complexes

Published in NASA Technical Reports Server, 2022

In this paper, we set out to give a novel semantics for modal logic in simplicial complexes. The motivation for this semantics will be first the replacement of possible worlds with the idea of an “agent perspective”. After exploring some of the philosophical implications of such a move, we give a semantics based around this idea. Following this, we explore some of the more interesting consequences of such a system, in particular the soundness of an unusual axiom we call NU^*. After giving soundness and completeness, we conclude by exploring ways to weaken this axiom in our semantics.

Recommended citation: Philip Sink (2022). "Modal Logic Without Possible Worlds: A New Semantics for Modal Logic in Simplicial Complexes" NASA Technical Reports Server
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A Note on Proper Relational Structures

Published in arXiv, 2025

In this note we provide an algorithm for translating relational structures into “proper” relational structures, i.e., those such that there is no pair of worlds \(w\) and \(u\) such that \(w\) is accessible from \(u\) for every agent. In particular, our method of translation preserves many classical properties of relational structures, such as transitivity and the Euclidean property. As a result, this method of translation has many applications in the literature on Simplicial Semantics for modal logic, where the creation of proper canonical relational structures is a common step in proofs of completeness.

Recommended citation: Adam Bjorndahl and Philip Sink (2025). "A Note on Proper Relational Structures" arXiv
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talks

A Logical Model of Pluralistic Ignorance

Published:

Much of the existing literature on pluralistic ignorance suggests that agents who find themselves in such a situation must consider themselves “special” in one way or another (Grosz 2018, Bjerring et al. 2014). Agents have to recognize their own dishonesty, but believe everyone around them is perfectly honest. This argument is taken to show that pluralistic ignorance is irrational. Modifying work from Christoff 2016, we use a simple logical model to show that these arguments for the irrationality of pluralistic ignorance depend on various introspection assumptions. We will finish by putting forth various scenarios where agents can be honest, headstrong, or something similar (generally taken to be impossible under pluralistic ignorance) but are nonetheless consistent if one relaxes introspection assumptions. This shows that agents can see themselves as no different from their friends and still be in a situation of pluralistic ignorance with sufficiently weak introspection assumptions.

Modal Logic Without Possible Worlds

Published:

Joint talk with Brittany Gelb. We presented a semantics for modal logic based on simplicial complexes that instead of possible worlds uses an “Agent Perspective”. Philip explained the details of the formalism, including a novel soundness and completeness proof. Brittany followed up with some applications of these models to a distributed setting. Additionally, she showed how we can use tools from algebraic topology to show a variety of things including the nonexistence of bisimulations.

Modal Logic Without Possible Worlds

Published:

Joint talk with Brittany Gelb. We presented a semantics for modal logic based on simplicial complexes that instead of possible worlds uses an “Agent Perspective”. Philip explained the details of the formalism, including a novel soundness and completeness proof. Brittany followed up with some applications of these models to a distributed setting. Additionally, she showed how we can use tools from algebraic topology to show a variety of things including the nonexistence of bisimulations.

Philosophy Then and Now: A Re-Evaluation of Rorty’s Philosophical Pessimism

Published:

This was a talk I was invited to give at a special session of the Richard Rorty Society by Dr. David Rondel. The main goal of the talk was to compare and contrast the metaphilosphies of Richard Rorty and Philip Kitcher, with the ultimate goal of showing that each has something to inform the other. In particular, each misses something of value the other catches. Rorty is ultimately overly skeptical of both formal philosophy, and both are overly skeptical of various politically motivated philosophical projects. However, Rorty’s views on this latter topic notably evolved in complex ways over time.

teaching

TA for 80-150 ‘‘Nature of Reason’’

Undergraduate course, Carnegie Mellon University, Department of Philosophy, 2021

TA for the course 80-150 ‘‘Nature of Reason’’, with Instructor of Record Dr. Francesca Zaffora Blando. Description from here.