There is not much room for originality in a historical and expository work of this kind, particularly as I believe in writing history objectively. I have not attempted to read into the mediæval thinkers modern ideas that were foreign to them. I endeavored to interpret their ideas from their own point of view as determined by their history and environment and the literary sources, religious and philosophical, under the influence of which they came. I based my book on a study of the original sources where they were available--and this applies to all the authors treated with the exception of the two Karaites, Joseph al Basir and Jeshua ben Judah, where I had to content myself with secondary sources and a few fragments of the original texts. For the rest I tried to tell my story as simply as I knew how, and I hope the reader will accept the book in the spirit in which it is offered--as an objective and not too critical exposition of Jewish rationalistic thought in the middle ages. My task would not be done were I not to express my obligations to the Publication Committee of the Jewish Publication Society of America to whose encouragement I owe the impulse but for which the book would not have been written, and whose material assistance enabled the publishers to bring out a book typographically so attractive. ISAAC HUSIK. PHILADELPHIA, _July, 1916._ TABLE OF CONTENTS PAGE PREFACE vii INTRODUCTION xiii CHAPTER I. ISAAC ISRAELI 1 II. DAVID BEN MERWAN AL MUKAMMAS 17 III. SAADIA BEN JOSEPH AL-FAYYUMI 23 IV. JOSEPH AL-BASIR AND JESHUA BEN JUDAH 48 V. SOLOMON IBN GABIROL 59 VI. BAHYA IBN PAKUDA 80 VII. PSEUDO-BAHYA 106 VIII. ABRAHAM BAR HIYYA 114 IX. JOSEPH IBN ZADDIK 125 X. JUDAH HALEVI 150 XI. MOSES AND ABRAHAM IBN EZRA 184 XII. ABRAHAM IBN DAUD 197 XIII. MOSES MAIMONIDES 236 XIV. HILLEL BEN SAMUEL 312 XV. LEVI BEN GERSON 328 XVI. AARON BEN ELIJAH OF NICOMEDIA 362 XVII. HASDAI BEN ABRAHAM CRESCAS 388 XVIII. JOSEPH ALBO 406 CONCLUSION 428