The idea to produce the current volume was conceived by Jiirgen Mittelstrass and Robert E. Butts in 1978. Idealist philosophers are wrong about one thing: the temporal gap separating idea and reality can be very long indeed - even ten or so years! Problems of timing were joined by personal problems and by the pressure of other professional commitments. Fortunately, James Brown agreed to cooperate in the editing of the volume; the infusion of his usual energy, good judgement and good-natured promptness saved the volume and made its produc­ tion possible. Despite the delays, the messages of the papers included in the book have not gone stale. An extremely worthwhile exercise in international philosophical cooperation has come to fruition; the German constructivist philosophical position is here represented in papers in English that will make its contemporary importance available to a larger audience. The editors owe thanks to many persons. All involved in the project owe much to the interest and support of Nicholas Rescher, a friend of the undertaking from the time of its inception. My review of the translations was helped immensely by Andrea Purvis' careful copy editing of the typescript. Most of all, however, we owe gratitude and admiration for the tireless efforts on behalf of this enterprise to Jiirgen Mittelstrass.

Section I: Constructivism and the logic of science.- Science, a Rational Enterprise?.- The Philosophy of Science and Its Logic.- The Pragmatic Understanding of Language and the Argumentative Function of Logic.- Rules versus Theorems.- On 'Transcendental'.- Section II: Constructivism and Protoscience.- Philosophy and the Problem of the Foundations of Mathematics.- Geometry as the Measure-Theoretic A Priori of Physics.- The Concept of Mass.- On the Definition of 'Probability'.- Section III: Constructivism and The Value Sciences.- Practical Reason and the Justification of Norms. Fundamental Problems in the Construction of a Theory of Practical Justification.- Protoethics: Towards a Formal Pragmatics of Justificatory Discourse.- Interests.- Is Rational Economics as an Empirical- Quantitative Science Possible?.- Determination by Reality or Construction of Reality?.- Notes On The Contributors.