ABSTRACT
THE most important ancient writing on the history of European thought was the Physical Opinions of Theophrastus.1 In this work of sixteen or eighteen books Theophrastus gave for the first time a systematic treatment of earlier views on the main problems of science and philosophy. Its influence in antiquity is attested by the frequency and respect with which it was referred to by later ancient writers. But its unique position was not fully appreciated by modern scholars until Usenerz collected the fragments of it and Diels scrutinized these fragments in relation to the large body of other doxographical writings. Diels proved that these writings, 1 The writer wishes to record his gratitude to Professors H. F. Cherniss and E. A. Havelock, who both urged the undertaking of this study and have generously read the manuscript and made many suggestions for its improvement.
