Is Understanding a Source of Epistemic Justification?

Célia Teixeira (Universidade Federal do Rio de Janeiro)

12 June 2026, 16:00 (Lisbon Time – WET)

Faculdade de Letras de Lisboa

Sala Mattos Romão [C201.J] (Departamento de Filosofia)

Abstract: The claim that understanding is a source of epistemic justification has been closely tied to the debate about the a priori. How do we know a priori truths such as that bachelors are unmarried, or that knowledge entails truth? According to a widely held view, we do so by understanding alone—and understanding is the source of the a priori. I examine this view. I begin by showing that it is ambiguous between semantic understanding and rational understanding. Focusing on the former, I distinguish a weak role for semantic understanding—on which it justifies beliefs about meaning—from a strong role—on which it justifies beliefs in non-semantic a priori truths. The weak role is uncontentious and unmysterious; the strong role is neither. I argue that semantic understanding might be the source of justification by which we know semantic truths, but not non-semantic a priori truths. For that, we need rational understanding. I then conclude by sketching an account of rational understanding as the source of most of our a priori knowledge.

Common Knowledge and Publicity

Sena Bozdag (University of Bayreuth)

5 June 2026, 16:00 (Lisbon Time – WET)

Faculdade de Letras de Lisboa

Sala Mattos Romão [C201.J] (Departamento de Filosofia)

Abstract: We study the relation between common knowledge and publicity, i.e. that certain events or facts are ”out in the open”, or ”public” in a group. Our contribution is conceptual and clarificatory. We point out, first, that while the iterative definition of common knowledge is central to the epistemic foundations of game theory, it is less so for theories of collective agency, that rather use “common knowledge” in the sense of publicity. Building on this observation, we propose to distinguish between internalist and externalist understandings of common knowledge and to associate the notion of publicity with the latter. This allows us to classify the different accounts of common knowledge that have by now been studied by logicians, game theorists, and philosophers, to defuse a recent debate in philosophy around the relation between common knowledge and publicity, and to put the emphasis on the conditions by which common knowledge and publicity emerge. (This is joint work with Olivier Roy.)

Abstraction Principles and Part-Whole: a Retrospective Survey

Paolo Mancosu (University of California, Berkeley)

29 May 2026, 17:00 (Lisbon Time – WET)

Faculdade de Letras de Lisboa

Sala Mattos Romão [C201.J] (Departamento de Filosofia)

Abstract: In this talk, I will give a survey of my work on the interaction between abstraction principles in neologicism and the part-whole property for Fregean concepts. Two Fregean concepts A and B stand in the relation of part-whole just in case the objects that fall under A are strictly included in the objects that fall under B. An abstraction principle with abstraction operator $ satisfies part-whole just in case it tracks the part-whole property, that is whenever A is strictly included in B then $(A)≠$(B). I will first discuss abstraction principles that satisfy part-whole and how they relate to the bad company objection for neologicism. Then I will look at principles that do not satisfy part-whole and how they relate to the good company objection for neologicism.

X Is Essentially F

Anna Marmodoro (Saint Louis University)

22 May 2026, 16:00 (Lisbon Time – WET)

Faculdade de Letras de Lisboa

Sala Mattos Romão [C201.J] (Departamento de Filosofia)

Abstract: In this paper I argue against the view that essences are related to the things that have them, as properties that things cannot lose without losing their identity. If things have their essences, regresses develop and unravel the ontology. Both Modal Essentialism and Kit Fine’s Definitional Essentialism are open to such regresses. By contrast, I advocate a type of essentialism according to which things do not have essences, and are not qualified by their essences, but rather, they are constituted of their essences.

The Difference Semantics for Conditionals

Hannes Leitgeb (University of Munich)

15 May 2026, 16:00 (Lisbon Time – WET)

Faculdade de Letras de Lisboa

Sala Mattos Romão [C201.J] (Departamento de Filosofia)

Abstract: In my talk I will present a new semantics for conditionals according to which “if A then B“ is true in case (i) the corresponding Stalnaker-Lewis conditional is true, and (ii) the antecedent A makes a difference to the consequent B. The novely of the semantics consists in the analysis of (ii), which is made precise as: the distance between the closest B-worlds and the closest non-B-worlds is smaller than the distance between the closest A&B-worlds and the closest A&non-B-worlds. I will explain how the required ordering of distances between worlds can be captured in non-numerical terms, what the logic is like that is sound and complete with respect to the semantics, what a probabilistic version of the semantics looks like, and why the system is to be preferred over other recent semantics and logics of conditionals that analyse (ii) above differently. (This is joint work with Hans Rott.)

Becoming Something Else

Elia Zardini (Complutense University of Madrid)

8 May 2026, 16:00 (Lisbon Time – WET)

Faculdade de Letras de Lisboa

Sala Mattos Romão [C201.J] (Departamento de Filosofia)

Abstract: This paper discusses a specific puzzle of change concerning what is the case in the result of change, as when e.g. a lump of clay becomes a statue of a boy. In the result of that change, it would seem that the lump has become the statue, and so that the lump is the statue. However, in what sense can a lump be a statue? After critically reviewing some natural and traditional views on the issue that weaken the sense in which, in the result of the change, the lump is the statue, I develop my own proposal, which vindicates that idea in its strongest sense, while respecting the platitude that nothing can be both a lump and a statue. The proposal starts with the idea that, in the result of the change, the state of affairs that x is the lump is unstable in that it determines the state of affairs that x is the statue. This metaphysical circumstance is then observed to give rise to the logical circumstance that contraction fails. By representing natural-language predications in terms of formal-language restricted universal quantifications, it is subsequently shown that the resulting system provides a theory on which indeed the lump is the statue while nothing can be both a lump and a statue. I close by drawing out some consequences that the proposal has for the notions of predication, existence and identity, and by indicating how it can be extended to deal with several other puzzles in the vicinity.

Concept Learning As Opening a Mental File

Nico Orlandi (University of California, Santa Cruz)

24 April 2026, 16:00 (Lisbon Time – WET)

Faculdade de Letras de Lisboa

Sala Mattos Romão [C201.J] (Departamento de Filosofia)

Abstract: Standard accounts of concepts in philosophy and in cognitive psychology hold that we learn a target concept by learning the concepts that constitute it. If this is the only model of learning we have, then only concepts that are complex or structured can be learned. I argue for an alternative to this framework by presenting a proposal for how we learn some atomic concepts. I show that we can learn a concept through descriptions without thinking that the concepts employed in the descriptions constitute the target concept. I develop this idea by using the notion of a mental file and by employing a general externalist explanatory strategy. In the view I develop, some concepts are akin to files in that the descriptions associated with a given concept are means of properly individuating the extension of the concept, and they are also means of connecting a concept to others, but they do not constitute the concept and can be revised or abandoned. I show how this discussion connects to issues in conceptual engineering.

This event is funded by Portuguese national funds through FCT – Fundação para a Ciência e a Tecnologia, I.P., within the project UID/00310/2025, Centro de Filosofia da Universidade de Lisboa (https://doi.org/10.54499/UIDB/00310/2025)

24-25 September 2026

School of Arts and Humanities

University of Lisbon

Speakers:

Katherine Puddifoot (University of Durham)

Jennifer Lackey (Northwestern University)

Lauren Leydon-Hardy (Amherst College)

Carolina Flores (LanCog)

Giada Fratantonio (LanCog)

Eleonora Volta (NOVA)

Rebecca Buxton (University of Bristol)

Organizer: Giada Fratantonio (LanCog, University of Lisbon)

This event is funded by Portuguese national funds through FCT – Fundação para a Ciência e a Tecnologia, I.P., within the project UID/00310/2025, Centro de Filosofia da Universidade de Lisboa (https://doi.org/10.54499/UIDB/00310/2025)

22-24 June 2026

Room A201 Anfiteatro III

School of Arts and Humanities

University of Lisbon

The 2026 LanCog Summer Metaphysics Workshop will be an intensive, three day workshop on metaphysics, and will feature leading scholars from around the world. Attendance is open to all who are interested, but anyone who is planning to attend should register for the workshop through the link below, so that the organizers can make sure there is enough coffee.

The 2026 LSMW will be an in-person event. There will, unfortunately, be no way to attend remotely.

Speakers:

Omobola Badejo (Obafemi Awolowo University)

Brigitte Everett (University of Sydney)

Akiko Frischhut (Sophia University)

Anna Giustina (University of Valencia)

Elton Junior Martins Marques (Federal University of Rio Grande do Norte)

Pedro Merlussi (Pontifical Catholic University of Rio de Janeiro)

Ricardo Santos (University of Lisbon)

Francisca Silva (University of St. Andrews)

David Yates (University of Lisbon)

TBD

Commentators:

Christabel Cane (University College London)

Jordi Castillo (University of Massachusetts Amherst)

Sharon Casu (University of Fribourg)

Gabriel Malagutti (LanCog, University of Lisbon)

Giorgio Lando (University of L’Aquila)

Min Ohn (University of Massachusetts Amherst)

Jeremy Pober (LanCog, University of Lisbon)

Mafalda Vale (LanCog, University of Lisbon)

Elle Walton (University of Massachusetts Amherst)

TBD

Register for the 2026 LanCog Summer Metaphysics Workshop

Co-Organizers: Ned Markosian (UMass Amherst, LanCog)

                            Hugo Luzio (LanCog, CFUL)

For any information or further queries about the workshop, please contact the organizers at the following email addresses: markosian@umass.edu or hugo.luzio@.edu.ulisboa.pt.

This event is funded by Portuguese national funds through FCT – Fundação para a Ciência e a Tecnologia, I.P., within the project UID/00310/2025, Centro de Filosofia da Universidade de Lisboa (https://doi.org/10.54499/UIDB/00310/2025)