First annotated edition of the important Karaite philosophical work of the Karaite scholar Aaron ben Elijah (c.1328–1369) by Franz Delitzsch with the assistance of M. Steinschneider. Ez Hayyim is part of Aaron’s greatest work, a massive Hebrew trilogy of Karaite learning, beginning with Ez Hayyim (“Tree of Life”). Composed in 1346, Ez Hayyim deals with the philosophy of religion. There is a forward and lengthy, primarily German prolegomena, and the text, which is in Hebrew. The book displays fully his great learning in both Karaite and Rabbanite literature. Aaron frequently quotes the Talmud, Saadia, Rashi, Abraham ibn Ezra, David Kimhi, Maimonides, Nahmanides, the earlier grammarians Judah ibn Quraysh, Judah Hayyuj, Jonah ibn Janah, and others. His Hebrew style, though strongly tinted with arabisms, is clear and fluent. Aaron is best known as a philosopher and the Ez Hayyim was undoubtedly undertaken by him with the aim of creating a Karaite counterpart to Maimonides' Guide of the Perplexed. Unlike Maimonides, Aaron did not venture to cut a new Aristotelian path for Karaite theological-philosophical thought. Instead, he remained attached to the Mu'tazilite philosophy (see Kalam) which dominated his Karaite predecessors, as well as a number of pre-Maimonidean Rabbanite philosophers. His Ez Hayyim. though written nearly two centuries after Maimonides' Guide, thus represents a step backward rather than forward. Aaron is more orderly, clear, and logical than his Karaite forerunners, but he merely restates what the latter had already said. That he realized this fact and felt uncomfortable about it seems evident from his occasional reluctance to take a definite stand on some points, nor could he refrain from adopting some Aristotelian terminology and argumentation. He consequently creates the impression that he really did not wholeheartedly believe in much of what he said, but regarded it as his duty to stand by the tradition of his predecessors.

Although Aaron had to deal with religion in a rational fashion, he begins his philosophical work with a wholesale condemnation of the Greek philosophers and of their brainchild, philosophy, in general. The teachings of the Mu'tazilite “investigators” (the term “philosopher” is objectionable to Aaron), on the other hand, are in accord with Scripture (as interpreted by the Karaites), while most Rabbanite thinkers, particularly Maimonides, follow the philosophers and thus often run counter to the true principles of the Torah. Reason is the chief instrument of true knowledge, hence God exists, for His existence was deduced rationally already by the patriarch Abraham. God is one, and is neither corporeal nor characterized by any corporeal qualities. His attributes are both negative and positive—indeed every negation implies a positive assertion—and not exclusively negative, as asserted by Maimonides. His providence and justice extend to all creatures, both human and subhuman. His revelations were given to His prophets for transmission to mankind as a guide to righteous life. The world (i.e., matter) is not eternal (as the Aristotelians taught) but created - this is the chief proof of God's existence - and consequently natural law is not immutable. The universe is made up of indivisible atoms having no magnitude and not eternal, and creation signifies combination of atoms, while dissolution signifies their separation. The atomic theory of matter, rejected by the Aristotelians, is thus reasserted by Aaron. Anthropomorphic descriptions of God in the Bible must be interpreted allegorically. God is all-knowing, but man's will is free, hence no evil can be charged to God; though God foreknows that the wicked will choose evil, the blame is theirs, not God's. Free will necessarily involves retribution according to each man's deserts. Scriptural ordinances are divided into revelational, whose necessity is so sublime that it is beyond rational explanation; and rational, whose necessity is deducible by reason. Good and evil are inherently so, and are not so merely because God approves of the former and condemns the latter. His approval or condemnation simply assist man in recognizing what is good and what is evil. Divine chastisement is not always punishment for antecedent sin: in the case of a righteous person like Job it is a Divine favor intended to increase the sufferer's reward in the world to come. Franz Delitzsch (Julius; 1813–1890) was a German Protestant theologian, Bible and Judaica scholar. Inspired by Julius Fuerst to devote himself to the study of Judaism, he was appointed professor of theology at the university of his native Leipzig in 1844. Later he taught at Rostock (1846), Erlangen (1850), and again in Leipzig (1867). Though Delitzsch was a devoted Protestant, believing in the supremacy of the New Testament over the Old, he maintained a genuine understanding of, and affection for, Judaism. Well versed in Hebrew and in Semitic languages, as well as in the Talmud and in medieval Jewish literature, Delitzsch was in close touch with the leading Jewish scholars of his time. As a devout Christian, he proselytized among the Jews, wrote several pamphlets for that purpose, and made a new translation of the New Testament into Hebrew (1877, 190112; supposedly with the assistance of A. H. Weiss). In 1863 he founded the missionary magazine, Saat und Hoffnung ("Seed and Hope"), which appeared regularly until 1935. In 1880 he established in Leipzig the Institutum Judaicum (renamed the "Delitzschianum" after his death), for the training of missionary workers among Jews, an institute which was still in existence in Muenster (Germany) in the 1970s. Nevertheless, Delitzsch fought vehemently against defamations of the Talmud by anti-Semitic writers, especially against Rohling's libelous pamphlet Der Talmudjude (1871). Delitzsch's first book, Zur Geschichte der juedischen Poesie vom Abschluss der Heiligen Schriften des Alten Bundes bis auf die neueste Zeit (1836), was the first comprehensive study of the history of Hebrew poetry and a serious attempt to deal with this subject with the accepted tools of literary criticism. In his Bible commentaries, the most important of which are those on Psalms (1859, 18945), on Isaiah (1866–18894), and on Ecclesiastes (1875), his approach was based upon philological analysis. He meticulously adhered to the masoretic text, and, on principle, avoided critical emendations. He mitigated his traditional attitude only in his later writings, in which he accepted some of the tenets of the "source theory" of modern Bible criticism.