Sergio Galvan is emeritus Professor of Logic at the Catholic University of Milan, Italy. His main areas of research are proof-theory and philosophical logic. In the first area he focuses on sequent calculi and natural deduction, the metamathematics of arithmetic systems (from Q to PA), Gödel's incompleteness theorems, and Gentzen's cut-elimination theorem. In the second area, his major interest is in the philosophical interpretations (deontic, epistemic and metaphysical) of modal logic. Recently, he has been working on the relationships between formal proof and intuition in mathematics, and on the metaphysics of essence and the ontology of possibilia.