Born in 1928 in Vantaa (Finland), he completed his intellectual training in his homeland and in the United States and holds various teaching positions in both countries. Author and co-author of more than thirty books and more than 300 articles, he made important contributions to logic, language theory, epistemology, the philosophy of mathematics and science, and the history of philosophy, including investigations on Aristotle, Descartes, Leibniz, Kant, Peirce and Wittgenstein. His works translated so far into Spanish are: Essays on explanation and understanding (1980), Logic, games of language and information (1976) and Knowledge and belief: an introduction to the logic of the two notions (1980).