Jean-Yves Beziau is Professor at the Federal University of Rio de Janeiro (UFRJ) and researcher of the Brazilian research council (CNPq). He has a PhD in philosopy and a PhD in mathematics. He has been working in France, Poland, Switzerland, Brazil and USA (Stanford and UCLA). He is Editor-in-Chief of the journal Logica Universalis. He has been working on the square of opposition since many years organizing world events on the subject. Dale Jacquette is ordentlicher Professor fur Philosophie, Abteilung Logik und theoretische Philosophie, Universitat Bern, Switzerland. He studied philosophy at Oberlin College (AB 1975) and Brown University (MA 1981, PhD 1983), and has worked on a variety of formal logical and philosophical projects related especially to the concept of intentionality. His research on the square of opposition is a result of converging interests in Aristotle's philosophy, intensional predicate term logics, and historical precursors of contemporary logic.

• 1 Historical and Critical Aspects of the Square.- 2 Philosophical Discussions around the Square of Opposition.- 3 The Square of Opposition and Non-Classical Logics.- 4 Constructions Generalizing the Square of Opposition.- 5 Applications of the Square of Opposition.

Jean-Yves Beziau is Professor at the Federal University of Rio de Janeiro (UFRJ) and researcher of the Brazilian research council (CNPq). He has a PhD in philosopy and a PhD in mathematics. He has been working in France, Poland, Switzerland, Brazil and USA (Stanford and UCLA). He is Editor-in-Chief of the journal Logica Universalis. He has been working on the square of opposition since many years organizing world events on the subject. Dale Jacquette is ordentlicher Professor fur Philosophie, Abteilung Logik und theoretische Philosophie, Universitat Bern, Switzerland. He studied philosophy at Oberlin College (AB 1975) and Brown University (MA 1981, PhD 1983), and has worked on a variety of formal logical and philosophical projects related especially to the concept of intentionality. His research on the square of opposition is a result of converging interests in Aristotle's philosophy, intensional predicate term logics, and historical precursors of contemporary logic.

• 1 Historical and Critical Aspects of the Square.- 2 Philosophical Discussions around the Square of Opposition.- 3 The Square of Opposition and Non-Classical Logics.- 4 Constructions Generalizing the Square of Opposition.- 5 Applications of the Square of Opposition.

Jean-Yves Beziau is Professor at the Federal University of Rio de Janeiro (UFRJ) and researcher of the Brazilian research council (CNPq). He has a PhD in philosopy and a PhD in mathematics. He has been working in France, Poland, Switzerland, Brazil and USA (Stanford and UCLA). He is Editor-in-Chief of the journal Logica Universalis. He has been working on the square of opposition since many years organizing world events on the subject. Dale Jacquette is ordentlicher Professor fur Philosophie, Abteilung Logik und theoretische Philosophie, Universitat Bern, Switzerland. He studied philosophy at Oberlin College (AB 1975) and Brown University (MA 1981, PhD 1983), and has worked on a variety of formal logical and philosophical projects related especially to the concept of intentionality. His research on the square of opposition is a result of converging interests in Aristotle's philosophy, intensional predicate term logics, and historical precursors of contemporary logic.

• 1 Historical and Critical Aspects of the Square.- 2 Philosophical Discussions around the Square of Opposition.- 3 The Square of Opposition and Non-Classical Logics.- 4 Constructions Generalizing the Square of Opposition.- 5 Applications of the Square of Opposition.