called in question, then naturally no fact, science, could be presupposed. Thus Plato was set on the path to the pure idea. Not gathered from the de facto sciences but formative of pure norms, his dialectic of pure ideas-as we say, his logic or his theory of science - was called on to make genuine 1 science possible now for the first time, to guide its practice. And precisely in fulfilling this vocation the Platonic dialectic actually helped create sciences in the pregnant sense, sciences that were consciously sustained by the idea of logical science and sought to actualize it so far as possible. Such were the strict mathematics and natural science whose further developments at higher stages are our modem sciences. But the original relationship between logic and science has undergone a remarkable reversal in modem times. The sciences made themselves independent. Without being able to satisfy completely the spirit of critical self-justification, they fashioned extremely differentiated methods, whose fruitfulness, it is true, was practically certain, but whose productivity was not clarified by ultimate insight. They fashioned these methods, not indeed with the everyday man's naivete, but still with a na!ivete of a higher level, which abandoned the appeal to the pure idea, the justifying of method by pure principles, according to ultimate a priori possibilities and necessities.

Situated at the crossroads of nature and culture, physics and consciousness, cosmos and life, history – intimately conjoined with time – continues to puzzle the philosopher as well as the scientist. Does brute nature unfold a history? Does human history have a telos? Does human existence have a purpose?

Substantial encouragement for this volume came from the editors and readers of the Studies for Phenomenological and Existential Philosophy (SPEP) at Northwestern University Press. But its publi­ cation has been made possible only by the unqualified and un­ abridged acceptance of the Editorial Board of Phaenomen%gica, which at the time was still headed by its founder, the late Professor H. L. Van Breda, who welcomed the manuscript most generously. This makes his untimely passing even more grievous to me. The stylistic copy editing and proof reading were handled ef­ ficiently by Ruth Nichols Jackson, secretary of the Philosophy Department. In the proof reading I also had the able help of my colleague Stanley Paulson. I dedicate this book to the memory of my late brother, Dr. chern. Erwin Spiegelberg, at the time of his death assistant professor at the University of Rio de Janeiro, who preceded me by two years in emigrating from Nazi Germany. When in 1938 he put an end to his life in an apparent depression, he also did so in order not to become a burden to his brothers, who were on the point of following him. Whatever I, more privileged in health and in opportunities in the country of my adoption, have been able to do and achieve since then has been done with a sense of a debt to him and of trying to live and work for him too.