2nd International Colloquium on Colours and Numbers

How Colours Matter for Philosophy

23rd - 26th March, 2015

Fortaleza, Brazil

Colours are so familiar for us that we cannot help wondering why they can be so troublesome and enigmatic for Philosophers. They can be found in many central problems in the History of Philosophy: from Aristotle examples for exclusions by contrariety and problems for the Principle of Excluded Middle to the collapse of Wittgenstein´s early Philosophy; from the discussion on the nature of secondary qualities in Modern Philosophy to more recent puzzles in the Hard Problem of Consciousness; from natural candidates for the synthetic a priori to the refusal of a sharp distinction between shape and content in Aesthetics; from challenges for an exclusive disjunction between subjectivity and objectivity to technical efforts to precisely express some inevitable vagueness of our language. Furthermore, colours are a kind of favourite example for many central philosophical arguments, which are used systematically to support some theses and to give some counterexamples to refute many other theories. Colours spur us to philosophize. The discussion on the nature of colours resides indeed in the core of many classical philosophical disputes, such as between Locke and Leibniz, Newton and Goethe and between Wittgenstein and himself. They represent problems to theories of perception and for rule-following, challenges to classical logical principles, illustration for harmonic and holistic systems, motivation for phenomenological arguments and modal systems of incompatibility, common ground to the Gestalt tradition and puzzles for some central accounts in Philosophy of Mind. In this sense, this Colloquium will examine and discuss different and seminal ways in which colours matter for Philosophy. Our Colloquium shall advance several discussions in different areas of Contemporary Philosophy and represent a comprehensive platform for further researches and collaboration programs. It will offer a forum for philosophers to interact across old disciplinary boundaries. The talks thereby delivered will be published in a book named “How Colours Matter for Philosophy”. This volume will be an essential resource for anyone working in some central areas of contemporary philosophy, and the starting point for future research in this fascinating field.

Date and Location

23rd - 26th March, 2015
Hotel Mareiro
Av. Beira Mar, 2380
Fortaleza, Brazil

Program Committee

André Leclerc, Aparecida Montenegro, Cícero Barroso, Joelma Marques, Marcos Silva, Nuno Venturinha, Francicleber Ferreira, Ana Teresa Martins, Carlos Fisch Brito

Organizing Committee

Tiago Magalhães, Juliana Brandão, Marcos Caetano, Yuri Rodrigues, Cristina Oliveira


Axel Barcelós (Mexico City)
Ori Beck (Pittsburgh)
Jean-Yves Beziau (San Diego)
Joao Vergílio Cuter (São Paulo)
Jairo da Silva (São Paulo)
Rogério Gerspacher (Belo Horizonte)
Dany Jaspers (Brussels)
André Leclerc (Fortaleza)
Andrew Lugg (Ottawa)
João Marcos (Natal)
Ingolf Max (Leipzig)
Anderson Luis Nakano (São Carlos)
Martina Nida-Rümelin (Fribourg)
Claudia Passos (Rio)
Luiz Carlos Pereira (Rio)
Graham Priest (New York)
Mihai Ometita (Norwich)
Diana Raffman (Toronto)
João Carlos Salles (Salvador)
Gisele Secco (Porto Alegre)
Marcos Silva (Fortaleza)
Pirmin Stekeler-Weithofer (Leipzig)
Ekai Txapartegegi (Basque Country)
Nicholas Unwin (Lancaster)

Contributed Papers

For proposals of contributed papers (slots of 30 and 45 minutes), please send an abstract with ca 500 words and a short CV until 15 January 25 January 2015 to Marcos Silva (marcossilvarj At gmail D0t com).

  • Extended deadline: 25 January 2015


Registration requests should sent by e-mail to coloursandnumbers2015ufc@gmail.com or can be done at the conference reception desk on arrival.

  • Early registration (until March 20th):
    • undergraduate students 20 reais
    • graduate students 40 reais
    • professors 100 reais
    • general public 40 reais

  • Late restristration (after March 20th):
    • undergraduate students 50 reais
    • graduate students 90 reais
    • professors 100 reais
    • general public 90 reais

Certificate of attendance after 70% of presence. Students from Ceará and Northeast part of Brazil are especially welcome!


Inscrições podem ser feitas através de e-mail para coloursandnumbers2015ufc@gmail.com ou na recepção na chegada para o evento.
  • Inscrição antecipada (até 20 de Março):
    • estudantes de graduação R$ 20
    • estudante de pós-graduação R$ 40
    • professores R$ 100
    • demais participantes R$ 40

  • Inscrição posterior (depois de 20 de Março):
    • estudantes de graduação R$ 50
    • estudante de pós-graduação R$ 90
    • professores R$ 100
    • demais participantes R$ 90

Certificado de participação requer mínimo de 70% de presença. Estudantes do Ceará e do Nordeste Brasileiro são especialmente bem-vindos!

Previous Event

The 1st International Colloquium on Colours and Numbers took place in 2013 in Fortaleza (see the brochure). Selected papers from the event has been published in a special issue of the Revista Argumentos, a journal run by the Post-Graduation Program of the Philosophy Department at the Universidade Federal do Ceará.


The four-day conference is open for all academic community. Graduate and Undergraduate Philosophy Students from Ceará and Northeast part of Brazil are especially welcome. We expect 24 talks of 50 minutes each + 20 minutes of discussion.


March 23th, 2015 – The Nature of Colours (Subjectivity X Objectivy)
Chair: Marcos Silva
14:00 - 15:00 Pirmin Stekeler-Weithofer: Subjectivity and Normativity in Colour Distinction
15:10 - 16:10 Ekai Txapartegi: Plato's Distinction between Hue, Saturation and Brightness [slides]
16:30 - 17:30 Jairo da Silva: Husserl on the material a priori - the question of colours
17:40 - 18:40 Andrew Lugg: Wittgenstein's treatment of colour and the naturalist's alternative [slides][pic]
March 24th, 2015 – The Logic of Colours (plus Philosophy of Language)
Chair: Francicleber Ferreira
09:30 - 10:30 Graham Priest: Contradiction, Dialetheism and Colour Sorites [slides]
10:40 - 11:40 Diana Raffman: Colours, Hats, and Hysteresis
11:50 - 12:50 Luiz Carlos Pereira and Gisele Secco: The Four-Colour Theorem and Four Relevant Consequences
15:00 - 16:00 Dany Jaspers: Colour in Cognition, Language and Philosophy
16:10 - 17:10 Jean-Yves Beziau: Interaction between Oppositions and Colours
17:20 - 18:20 João Marcos: Notes Regarding a Colourful Metalogic
March 25th, 2015 – The Phenomenology of Colours (plus Philosophy of Mind)
Chair: Carlos Brito
Morning Free
14:00 - 15:00 Martine Nida-Rümelin: The special role of colours in perceptual experience [slides]
15:10 - 16:10 Nicholas Unwin: Explaining Colour Phenomenology [slides]
16:20 - 16:50 Rogério Gerspacher: The mathematical nature of physical laws and the explanatory gap
17:00 - 17:30 Ori Beck: How Inverted Spectra Can Colour Your Beliefs [slides]
17:50 - 18:50 Claudia Passos-Ferreira: Colour experience in newborn babies: A problem for representationalism?
19:00 - 20:00 André Leclerc: Reassessing Discussions on Colour-dispositionalism
March 26th, 2015 – Wittgenstein (From the Tractatus to the Bemerkungen über Farben)
Chair: André Leclerc
09:30 - 10:30 João Vergílio Cuter: The Coordinate Space of Colours
10:40 - 11:40 Marcos Silva: On a philosophical motivation for mutilating truth tables [slides]
12:00 - 13:00 Axel Barcelós: Wittgenstein on Colour [slides]
15:00 - 16:00 João Carlos Salles: On Certainty and on Colours
16:10 - 16:40 Mihai Ometita: Phenomenology as Logic of Content: Wittgenstein, Ramsey, and Schlick on Colour Exclusion
16:50 - 17:20 Anderson Luis Nakano: Remarks on the relation between the logical analysis of visual space and the “new theory of generality” in Wittgenstein’s Philosophical Remarks [slides]
17:30 - 18:30 Ingolf Max: The harmony of colour concepts – bridging the early and the late Wittgenstein


For further information, please contact marcossilvarj At gmail D0t com