Jewish philosophy refers to the conjunction between serious study of philosophy and Jewish theology. According to Jewish tradition, Abraham was a trained astronomer who arrived at a belief in monotheism on purely philosophical grounds before receiving any prophetic revelation from God. The Book of Psalms contains appeals to philosophical speculation, such as invitations to admire the wisdom of God through his works. Other books of philosophical interest are Proverbs and Ecclesiastes.

The Jewish philosophers of the Arab-speaking world were the humanists of the Middle Ages. The scholastics preserved the continuity of philosophical thought of the Torah. Without the activity of these Arabic-Jewish philosophers, the culture of the Western world could scarcely have taken the direction it has, which was made possible through the agency of the Humanists and of the Renaissance. They established and maintained the bond of union between the Arabic philosophers, physicians, and poets on the one hand, and the Latin-Christian world on the other. Saadia Gaon, Gersonides, Gabirol, Maimonides, and Crescas are considered of eminent importance in the continuity of philosophy, for they not only illumined Christian scholasticism, but their light has penetrated deeply into the philosophy of modern times.

Among Jewish thinkers who had this view one may note Saadia Gaon, Gersonides, and Abraham Ibn Daud. In this latter case a religious person would also be a philosopher, by asking questions such as:

1. What is the nature of G-d?
2. How do we know that God exists?
3. What is the nature of revelation?
4. How do we know that God reveals his will to mankind?
5. Which of our religious traditions must be interpreted literally?
6. Which of our religious traditions must be interpreted allegorically?
7. What must one actually believe to be considered a true adherent of our religion?
8. How can one reconcile the findings of philosophy with religion?
9. How can one reconcile the findings of science with religion?

Jewish philosophy is philosophical inquiry informed by the texts, traditions and experiences of the Jewish people. Its concerns range from the farthest reaches of cosmological speculation to the most intimate drama of ethical choice and the forum of political debate. Jewish tradition contains insights and articulates values of lasting philosophical import. These ideas and values are articulated in a variety of idioms, from the mythic and archetypal discourse of the Book of Genesis to the ethical and legislative prescriptions of the Pentateuch; to the writings of the Prophets; the juridical and allegorical midrash and dialectics of the Rabbis.

The confidence of the practitioners of Jewish philosophy is the conceptual vitality and continually renewed moral and spiritual relevance of the tradition which reflects a commitment to that tradition and to the people who are its bearers. That confidence and by the richness of the tradition itself, is the renewal and encouragement for the commitment especially in times of historical crisis and external pressures. It address’ the wisdom of a covenant between the universal G-d and the people of Israel, the meaning of that people’s mission, their chosen purpose, their distinctive laws, customs and traditions; and the relation of those norms to the more widely recognized norms of humanity, of which the Prophets of Israel were early and insistent messengers.

Jewish philosophy has made and continues to make a distinctive contribution to philosophical discourse in this regard. It shares the problems of Western philosophy but offers a distinctive perspective that calls into question accepted verities and therefore enhances the critical edge of philosophical work for those who study it. Jewish philosophy has over the course of its history been the source of study based on the philosophically relevant ideas of the Hebrew Bible.

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Philo of Alexandria (20 BCE – 40 CE) was a Hellenized Jewish philosopher born in Alexandria, Egypt: The first exponent of Jewish philosophy was Philo of Alexandria, a major contributor to the synthesis of Stoicism, Middle Platonism and monotheistic ideas that helped forge the tradition of scriptural philosophy in the West. Philo included in his philosophy both the wisdom of Ancient Greece and Judaism, which he sought to fuse and harmonize by means of the art of allegory that he had learned as much from Jewish exegesis as from the Stoics. His work was not widely accepted in Judaism, though it later became important to Christian theologians. Philo made his philosophy the means of defending and justifying Jewish religious truths. These truths he regarded as fixed and determinate; and philosophy was used as an aid to truth, and as a means of arriving at it. With this end in view Philo chose from the philosophical tenets of the Greeks, refusing those that did not harmonize with the Jewish religion, as, e.g., the Aristotelian doctrine of the eternity and indestructibility of the world.

Early Jewish philosophy was heavily influenced by the philosophy of Plato, Aristotle and Islamic philosophy. Many early medieval Jewish philosophers (from the 8th century to end of the 9th century) were especially influenced by the Islamic Mutazilite philosophers; they denied all limiting attributes of God and were champions of God’s unity and justice.

Al-Fayyumi Saadiah Gaon (882–942), the first systematic Jewish philosopher, was also a major biblical translator and exegete, a grammarian, lexicographer and authority on Jewish religious law and ritual. The rationalism, pluralism and intellectual honesty evident in his work made it a model of Jewish philosophy for all who came after him. Saadia Gaon is considered one of the greatest of the early Jewish philosophers. His Emunoth ve-Deoth (Beliefs and opinions) was originally called Kitab al-Amanat wal-l’tikadat, the “Book of the Articles of Faith and Doctrines of Dogma”. It was the first systematic presentation and philosophic foundation of the dogmas of Judaism, completed in 933.

In the scheme of his work Saadia contributed to the Mutazilites (the rationalistic dogmatists of Islam) relative to the Mutazilite school of Al-Jubbai. He followed the Mutazilite Kalam, especially in this respect, that in the first two sections he discussed the metaphysical problems of the creation of the world (i.) and the unity of God (ii.), while in the following sections he treated of the Jewish theory of revelation (iii.) and of the doctrines of belief based upon divine justice, including obedience and disobedience (iv.), as well as merit and demerit (v.). Closely connected with these sections are those which treat of the soul and of death (vi.), and of the resurrection of the dead (vii.), which, according to the author, forms part of the theory of the Messianic redemption (viii.). The work concludes with a section on the rewards and punishments of the future life (ix.)

Other early figures include Daud al-Muqammas and Isaac Israeli, two of the first figures of medieval Jewish philosophical theology.

Avicebron, Solomon ibn Gabirol: The Jewish poet-philosopher Solomon Ibn Gabirol is also known as Avicebron. He died about 1070 CE. He was influenced by Plato. His classic work on philosophy was Mekor Chayim, “The Source of Life”. His work on ethics is entitled Tikkun Middot HaNefesh, “Correcting the Qualities of the Soul”.

In Gabirol’s work Plato is the only philosopher referred to by name. Characteristic of the philosophy of both is the conception of a Middle Being between God and the world, between species and individual. Aristotle had already formulated the objection to the Platonic theory of ideas, that it lacked an intermediary or third being between God and the universe, between form and matter. This “third man,” this link between incorporeal substances (ideas) and idealess bodies (matter), is, with Philo, the Logos; with Gabirol it is the divine will. Philo gives the problem an intellectual aspect; while Gabirol conceives it as a matter of volition, approximating thus to such modern thinkers as Schopenhauer and Wundt.

Gabirol was one of the first teachers of Neoplatonism in Europe. His role has been compared to that of Philo. Philo had served as the intermediary between Greek philosophy and the Oriental world; a thousand years later Gabirol occidentalized Greco-Arabic philosophy and restored it to Europe. The philosophical teachings of Philo and Ibn Gabirol were largely ignored by their fellow Jews; the parallel may be extended by adding that Philo and Gabirol alike exercised a considerable influence in extra-Jewish circles: Philo upon early Christianity, and Ibn Gabirol upon the scholasticism of medieval Christianity.

Gabirol’s philosophy made little impression on later Jewish philosophers. His greatest impact is in the area of the Jewish liturgy. His work is quoted by Moses ibn Ezra and Abraham ibn Ezra. Christian scholastics, including Albertus Magnus and his pupil, Thomas Aquinas, defer to him frequently and gratefully.

Karaite philosophy: A sect which rejects the Rabbinical Works, Karaism, developed its own form of philosophy, a Jewish version of the Islamic Kalâm. Early Karaites based their philosophy on the Islamic Motazilite Kalâm; some later Karaites, such as Aaron ben Elijah of Nicomedia (fourteenth century), reverted, in his Etz Hayyim (Hebrew, “Tree of Life”) to the views of Aristotle.

Bahya ibn Paquda lived in Spain in the first half of the eleventh century. He was the author of the first Jewish system of ethics, written in Arabic in 1040 under the title Al Hidayah ila Faraid al-hulub, “Guide to the Duties of the Heart”, and translated into Hebrew by Judah ben Saul ibn Tibbon in 1161-1180 under the title Chovot ha-Levavot, ‘Duties of the Heart’.

Though he quotes Saadia Gaon’s works frequently, he belongs not to the rationalistic school of the Motazilities whom Saadia follows, but, like his somewhat younger contemporary, Solomon ibn Gabirol (1021-1070), is an adherent of Neoplatonic mysticism. He often followed the method of the Arabian encyclopedists known as “the Brethren of Purity”. Inclined to contemplative mysticism and asceticism, Bahya eliminated from his system every element that he felt might obscure monotheism, or might interfere with Jewish law. He wanted to present a religious system at once lofty and pure and in full accord with reason.

Yehuda Halevi and the Kuzari: The Jewish poet-philosopher Yehuda Halevi (twelfth century) in his polemical work Kuzari made strenuous arguments against philosophy. He became thus the Jewish Al-Ghazali, whose The Incoherence of the Philosophers was perhaps the model for the Kuzari. Human reason on a surface level, at any rate as expressed in the philosophy of Aristotle and Avicenna, is considered false and illusory; rather inward illumination based on truths instilled by God in the human soul is considered paramount. The Kuzari describes representatives of different religions and of philosophy disputing before the king of the Khazars concerning the respective merits of the systems they stand for, the victory being ultimately awarded to Judaism.Judah ha-Levi could not bar the progress of Aristotelianism among the Arabic-writing Jews. As among the Arabs, Avicenna and Averroes leaned more and more on Aristotle, so among the Jews did Abraham ibn Daud and Maimonides.

Rabbi Moshe ben Maimon (1135 – 1204) known commonly by his Greek name Maimonides, was a Jewish rabbi, physician, and philosopher. Maimonides held that no positive attributes can be predicated to God. The number of His attributes would seem to prejudice the unity of God. In order to preserve this doctrine undiminished, all anthropomorphic attributes, such as existence, life, power, will, knowledge – the usual positive attributes of God in the Kalâm – must be avoided in speaking of Him. Between the attributes of God and those of man there is no other similarity than one of words (homonymy), no similarity of essence (“Guide,” I 35, 56). The negative attributes imply that nothing can be known concerning the true being of God, which is what Maimonides really means. Just as Kant declares the Thing-in-itself to be unknowable, so Maimonides declares that of God it can only be said that He is, not what He is.

Maimonides wrote his thirteen principles of faith, which he stated that all Jews were obligated to believe. The first five deal with knowledge of the Creator. The next four deal with prophecy and the Divine Origin of the Torah. The last four deal with Reward, Punishment and the ultimate redemption. The principle which inspired all of Maimonides’ philosophical activity was identical with the fundamental tenet of Scholasticism: there can be no contradiction between the truths which G-d has revealed and the findings of the human mind in science and philosophy. Moreover, by science and philosophy he understood the science and philosophy of Aristotle. In some important points, however, he departed from the teaching of the Aristotelian text, holding, for instance, that the world is not eternal, as Aristotle taught, but was created ex nihilo, as is taught explicitly in the Bible. Again, he rejected the Aristotelian doctrine that God’s provident care extends only to humanity, and not to the individual. But, while in these important points Maimonides anticipated the Scholastics and possibly influenced them, he was led by his admiration for the neo-Platonic commentators and by the bent of his own mind to maintain many doctrines which the Scholastics could not accept.

Jewish philosophy after Maimonides: Rabbi Levi ben Gershon, also known as Gersonides, or the Ralbag, (1288-1345) is best known for his work Milhamot HaShem (or just Milchamot), (“Wars of the Lord”). Among scholastics, Gersonides was perhaps the most advanced; he placed reason above tradition. The Milhamot HaShem is modelled after the Guide for the Perplexed of Maimonides. It may be seen as an elaborate criticism from a philosophical point of view (mainly Averroistic) of the syncretism of Aristotelianism and Jewish orthodoxy as presented in that work.

Hasdai Crescas (1340-1410) is best known for his Or Hashem (“Light of the Lord”). Crescas’ avowed purpose was to liberate Judaism from what he saw as the bondage of Aristotelianism, which, through Maimonides, influenced by Ibn Sina, and Gersonides (Ralbag), influenced by Ibn Roshd (Averroes) threatened to blur the distinctness of the Jewish faith, reducing the doctrinal contents of Judaism to a surrogate of Aristotelian concepts. His book, Or Hashem, comprises four main divisions (ma’amar), subdivided into kelalim and chapters (perakim): the first treating of the foundation of all belief—the existence of God; the second, of the fundamental doctrines of the faith; the third, of other doctrines which, though not fundamental, are binding on every adherent of Judaism; the fourth, of doctrines which, though traditional, are without obligatory character, and which are open to philosophical construction.

Joseph Albo was a Spanish rabbi, and theologian of the fifteenth century, known chiefly as the author of the work on the Jewish principles of faith, his Ikkarim. Albo limited the fundamental Jewish principles of faith to three: (1) The belief in the existence of God; (2) in revelation; and (3) in divine justice, as related to the idea of immortality. Albo finds opportunity to criticize the opinions of his predecessors, yet he takes pains to avoid heresy hunting. A remarkable latitude of interpretation is allowed; so much so, that it would indeed be difficult under Albo’s theories to impugn the orthodoxy of even the most theologically liberal Jews. Albo rejects the assumption that creation ex nihilo is an essential implication of the belief in God. Albo freely criticizes Maimonides’ thirteen principles of belief and Crescas’ six principles.

Isaac Abravanel commented on Maimonides’ thirteen principles in his Rosh Amanah. According to him, if one must reduce Judaism to a set of credal propositions, Maimonides’ attempt cannot be improved upon. At the same time, the actually binding part of Judaism is the entire body of 613 mitzvot rather than any set of beliefs.

Jewish Mysticism, Kabbalah: The general difference between the Kabbalists and exponents of Philosophy is due to their different views of the power of human intellect from first principles in apprehending the Divine. Kabbalists accept the conclusions of unaided reason in support of the Torah in general, such as the teachings of Maimonides, but hold that the Divine transcendent levels themselves can only be articulated by the mystical, hidden level of Torah interpretation, which is governed by its own traditional system of hermeneutics. This is wisdom from revelation (“God’s intellect” as it were), rather than unaided intellect (man’s intellect). The Jewish mystical tradition claims to originate in the prophetic traditions of the Bible, and became expressed in developing conceptual form. With its wide dissemination in the Jewish world of the late Middle Ages, it became the mainstream Jewish theology, sidelining the earlier school of Philosophy that had expressed Jewish belief in the framework of Greek thought. Philosophers, on the other hand, hold that human intellect from first principles is the requisit path to perception and knowledge, though the great medieval Jewish philosophers also believed that there is an authentic mystical level to the Torah. See Hasidic philosophy below for the later development of the Jewish mystical tradition that unites the two realms.

Renaissance Jewish philosophy: Classical Judaism saw the development of a brand of Jewish philosophy drawing on the teachings of Torah mysticism derived from the esoteric teachings of the Zohar and the teachings of Rabbi Isaac Luria. This was particularly embodied in the voluminous works of Rabbi Judah Loew ben Bezalel known as the Maharal of Prague.

One work that gained considerable influence in the Christian world was the Dialoghi d’Amore of Judah Leon Abravanel (known as Leone Ebreo). This took the form of a series of dialogues between “Philo” and “Sophia”, and may be compared with the Renaissance Platonism of Ficino and Pico della Mirandola, but had no explicit Jewish content. Blends between Kabbalah and Italian Platonism are found in later Jewish thinkers, most explicitly in Moses Chaim Luzzatto (in particular his Derech ha-Elohim, “the Way of God”). This kind of thought also forms the background to thinkers such as Isaiah Horowitz (the Shene Luchot ha-Berit) and Aryeh Leib Heller and had some influence on the Tanya.

Enlightenment Jewish philosophers: Baruch Spinoza adopted Pantheism and broke with Orthodox Judaism. Nevertheless the Jewish influence in his work, for example from Maimonides and Leone Ebreo, is evident. Some contemporary critics (e.g. Wachter, Der Spinozismus im Judenthum) claimed to detect the influence of the Kabbalah, while others (e.g. Leibniz) regarded Spinozism as a revival of Averroism. Moses Mendelssohn sought to harmonize Judaism with the teachings of the Enlightenment. He believed that the theological content of Judaism did not go beyond “natural theology”, and that Judaism as such was not revealed religion but revealed legislation.

Modern Jewish philosophy: Modern Jewish philosophers: The following philosophers have had a substantial impact on the philosophy of modern day Jews who identify as such. They are writers who consciously dealt with philosophical issues from within a Jewish framework. One of the major trends in modern Jewish philosophy was the attempt to develop a theory of Judaism through existentialism. One of the primary players in this field was Franz Rosenzweig. While researching his doctoral dissertation on the 19th-century German philosopher Georg Wilhelm Friedrich Hegel, Rosenzweig reacted against Hegel’s idealism and favored an existential approach. Rosenzweig, for a time, considered conversion to Christianity, but in 1913, he turned to Jewish philosophy. He became a philosopher and student of Hermann Cohen. Rozensweig’s major work, Star of Redemption, is his new philosophy in which he portrays the relationships between God, humanity and world as they are connected by creation, revelation and redemption. Later Jewish existentialists include Conservative rabbis Neil Gillman and Elliot N. Dorff.

Perhaps the most controversial form of Jewish philosophy that developed in the early 20th century was the religious naturalism of Rabbi Mordecai Kaplan. His theology was a variant of John Dewey’s philosophy. Dewey’s naturalism combined atheist beliefs with religious terminology in order to construct a religiously satisfying philosophy for those who had lost faith in traditional religion. In agreement with the classical medieval Jewish thinkers, Kaplan affirmed that God is not personal, and that all anthropomorphic descriptions of God are, at best, imperfect metaphors. Kaplan’s theology went beyond this to claim that God is the sum of all natural processes that allow man to become self-fulfilled. Kaplan wrote that “to believe in God means to take for granted that it is man’s destiny to rise above the brute and to eliminate all forms of violence and exploitation from human society.”

One of the more recent trends has been a reframing of Jewish theology through the lens of process philosophy, and more specifically process theology. Process philosophy suggests that fundamental elements of the universe are occasions of experience. According to this notion, what people commonly think of as concrete objects are actually successions of these occasions of experience. Occasions of experience can be collected into groupings; something complex such as a human being is thus a grouping of many smaller occasions of experience. In this view, everything in the universe is characterized by experience (which is not to be confused with consciousness); there is no mind-body duality under this system, because “mind” is simply seen as a very developed kind of experiencing.

Inherent to this worldview is the notion that all experiences are influenced by prior experiences, and will influence all future experiences. This process of influencing is never deterministic; an occasion of experience consists of a process of prehending other experiences, and then a reaction to it. This is the process in process philosophy. Process philosophy gives God a special place in the universe of occasions of experience. God encompasses all the other occasions of experience but also transcends them; thus process philosophy is a form of panentheism.

The original ideas of process theology were developed by Charles Hartshorne (1897-2000), and influenced a number of Jewish theologians, including British philosopher Samuel Alexander (1859-1938), and Rabbis Max Kaddushin, Milton Steinberg and Levi A. Olan, Harry Slominsky and to a lesser degree, Abraham Joshua Heschel. Today some rabbis who advocate some form of process theology include Donald B. Rossoff, William E. Kaufman, Harold Kushner, Anton Laytner, Gilbert S. Rosenthal, Lawrence Troster and Nahum Ward.

Perhaps the most unexpected change in Jewish religious thinking in the late 20th century was the resurgence of interest in Kabbalah. Many philosophers do not consider this to be a form of philosophy, as Kabbalah is a form of mysticism. Mysticism is generally understood as an alternative to philosophy, and not a variant of philosophy.

Solomon ibn Gabirol (c.1020–c.1057), long known as a Hebrew poet, was discovered in the nineteenth century to have been the author as well of the famous Neoplatonic philosophical work, preserved in Latin as the Fons Vitae. Moses ibn Ezra (c.1055–after 1135) is notable for his poetic and philosophic conributions. Abraham ibn Ezra (c.1089–1164) is likewise noted for his hermeneutical ideas and methods; his forthright approach to the Hebrew Bible was a critical influence on the thinking of Jewish philosophers from the Middle Ages to Spinoza and beyond. A less familiar figure is Abu ’l-Barakat al-Baghdadi (fl. c.1200–50), a brilliant Jewish thinker who converted to Islam late in life. He developed highly independent views about the nature of time, human consciousness, space, matter and motion. His work undercuts the notion that the medieval period was simply an age of faith and static commitment to a faith community.

A polymath of rather different spirit was Abraham bar Hayya in the eleventh century, who wrote on astronomy, mathematics, geography, optics and music as well as philosophy and who collaborated on scientific translations with the Christian scholar Plato of Tivoli, the transmitter of the Ptolemaic system to the Latin world. Bar Hayya’s Meditation of the Sad Soul expresses the forlornness of human life in exile from the world of the divine, a forlornness tinged with the hope of future glory. Joseph ibn Tzaddik (d. 1149) similarly developed Neoplatonic ideas around the theme of the human being as a microcosm.

Bahya ibn Pakuda (early twelfth century) wrote as a pietist philosopher. He placed philosophical understanding and critical thinking at the core of the spiritual devotion called for by the sincerest form of piety. Judah Halevi (before 1075–1141), probably the greatest Hebrew poet after the Psalms, wrote a cogently argued philosophical dialogue best known as the Kuzari, but more formally titled, A Defence and an Argument in behalf of the Abased Religion. Set in the Khazar kingdom, whose king, historically, had converted to Judaism, the work mounts a trenchant critique of the intellectualism of the prevalent philosophical school and the spiritualizing and universalizing ascetic pietism that was its counterpart. Calling for a robust recovery of Jewish life and peoplehood in the Land of Israel, the work is not only a striking anticipation of Zionist ideas but a remarkable expression of the need to reintegrate the spiritual, intellectual, moral and physical dimensions of Jewish life.

Abraham ibn Daud (c.1110–80), a historian as well as a philosopher, used his historiography to argue for the providential continuity of the Jewish intellectual and religious tradition. His philosophical work laid the technical foundations that made possible the philosophical achievement of Moses Maimonides (1138–1204), the greatest of the philosophers committed to the Jewish tradition. Besides his medical writings and his extensive juridical corpus, which includes the authoritative fourteen-volume code of Jewish law, the Mishneh Torah, Maimonides was the author of the famous Guide to the Perplexed. Written in Arabic and intended for an inquirer puzzled by the apparent discrepancies between traditional Judaism and Aristotelian-Neoplatonic philosophy, the Guide is a paradigm in the theology of transcendence, addressing questions ranging from the overt anthropomorphism of the scriptural text to the purposes of the Mosaic legislation, to the controversy over the creation or eternity of the world, the problem of evil, and the sense that can be made of the ideas of revelation, providence, divine knowledge and human perfectibility. Like Halevi’s Kuzari and Bahya’s Duties of the Heart, the Guide to the Perplexed continues to be studied to this day by Jews and non-Jews for its philosophical insights.

Abraham ben Moses Maimonides (1186–1237), the son of the great philosopher and jurist, began his scholarly life as a defender of his father’s work against the many critics who feared Maimonidean rationalism. In his mature work he became the exponent of a mystical, pietist and ascetic movement, largely influenced by Sufism. Moses Nahmanides (1194–1270), exegete, theologian and a founding figure of the Kabbalistic theosophy, championed Judaism in the infamous Barcelona Disputation of 1263 and played a leading role in the Maimonidean controversy. He struggled to harmonize his conservative and reactive tendencies with his respect for reason and the unvarnished sense of the biblical text.

Ibn Kammuna (d. 1284) was a pioneer in other areas. Besides his work in the Ishraqi or Illuminationist tradition of theosophy, laid out in commentary on the Muslim philosopher Ibn Sina (Avicenna), he wrote a distinctively dispassionate study of comparative religions, favouring Judaism but fairly and unpolemically presenting the Christian and Muslim alternatives.

Shem Tov ibn Falaquera (c.1225–c.1295) was a warm exponent of Maimonidean rationalism and an ardent believer in the interdependence of faith and reason. His selections in Hebrew from the lost Arabic original of Ibn Gabirol’s magnum opus allowed modern scholars to identify Ibn Gabirol as the Avicebrol of the surviving Latin text, the Fons Vitae.

Hillel ben Samuel of Verona (c.1220–95), physician, translator, Talmudist and philosopher was a Maimonist who introduced numerous scholastic ideas into Hebrew philosophical discourse. Immanuel of Rome (c.1261–before 1336) was a prolific author of philosophical poetry and exegesis, often praising reason and intellectual love. Judah ben Moses of Rome (c.1292–after 1330), known as Judah Romano, was an active bridge person between the Judaeo-Arabic and the scholastic tradition of philosophical theology.

Levi ben Gershom, known as Gersonides (1288–1344), was an important astronomer and mathematician as well as a biblical exegete and philosopher. His Wars of the Lord grappled with the problems of creation, providence, divine knowledge, human freedom and immortality. Aiming to defend his ancestral faith, Gersonides followed courageously where the argument led, often into radical and creative departures from traditional views.

Hasdai Crescas (1340–1410), an ardent defender of Judaism against Christian conversionary pressures, was among the most creative figures of Jewish philosophy, challenging many of the givens of Aristotelianism, including the idea that the cosmos must be finite in extent. Crescas’ student Joseph Albo (c.1360–1444) sought to organize Jewish theology into an axiomatic system, in part to render Jewish thought defensible against hostile critics.

Profiat Duran (d. c. 1414), also known as Efodi, used his extensive understanding of Christian culture to criticize Christianity from a Jewish perspective. Deeply influenced by Moses Maimonides and Abraham ibn Ezra and by Neoplatonic and astrological ideas, he sought to balance the practical with the intellectual aspects of the Torah. Simeon ben Tzemach Duran (1361–1444) contributed an original approach to the project of Jewish dogmatics and an implicit critical examination of that project.

The Shem Tov family included four thinkers active in fifteenth century Spain. Their works follow the persecution of 1391 and the ensuing mass apostasy of Spanish Jews and seek to rethink the relations of philosophy to Judaism. Shem Tov, the paterfamilias, criticized Maimonides and endorsed Kabbalah, but his sons Joseph, a court physician and auditor of royal accounts at Castile, and Isaac, a popular teacher of Aristotelian philosophy, and Joseph’s son, again named Shem Tov, wrote numerous Peripatetic commentaries. These offspring charted a more moderate course that enabled Jewish intellectuals to cultivate philosophy and the kindred arts and sciences while asserting the ultimate primacy of their revealed faith.

Isaac ben Moses Arama (c.1420–94), like Nahmanides, was critical of Maimonidean and Aristotelian rationalism but did not discard reason, seeing in it a crucial exegetical tool and an avenue toward understanding miracles and providence. Isaac Abravanel (1437–1508), leader of the Jews whom Ferdinand and Isabella exiled from Spain in 1492, like Arama criticised Maimonidean rationalism in the interest of traditional Judaism as he saw it, but at the same time put forward a theistic vision of history and strikingly modern views about politics and the state. His son, Judah ben Isaac Abravanel, also known as Leone Ebreo (c.1460–c.1521), wrote the Dialoghi d’amore. Couched in the language of courtly love, the work explores the idea that love is the animating force of the cosmos. The work stands out as a brilliant dialectical exploration of the differences and complementarities of the Platonic and Aristotelian approaches to philosophy.

Judah Messer Leon (c.1425–c.1495) was a philosopher, physician, jurist, communal leader, poet and orator. Awarded a doctorate in medicine and philosophy by the Emperor Frederick III, he could confer doctoral degrees in those subjects on the students in his yeshivah. He saw logic as the key to harmonizing religion and philosophy and favored scholastic logic over the Arabic logical works. His encyclopedia became a popular textbook, and his systematic elicitation of Hebrew rhetoric from the biblical text, in The Book of the Honeycomb’s Flow, one of the first Hebrew books to be printed, was a masterpiece of cross-cultural humanistic scholarship. But Messer Leon failed to curb the spread of Kabbalah, whose underlying Platonic metaphysics he abhorred and whose appropriation by Christian Platonists he held in deep suspicion. Indeed, his own son turned toward the Kabbalah and sought to combine its teachings with the Aristotelianism favored by his father.

Yohanan ben Isaac Alemanno (1433/4–after 1503/4) brought together in his thinking Averroist, Kabbalistic, Neoplatonic and Renaissance humanist themes. He instructed Pico della Mirandola in Hebrew and in Kabbalah, bringing to birth what became a Christian, syncretic Kabbalism. Elijah Delmedigo (c.1460–93) was an Aristotelian and Averroist. He translated works into Latin for Pico della Mirandola and developed a subtle critique of the kabbalistic ideas that in his time were rivaling and often displacing what he saw as more disciplined philosophical thinking. Abraham Cohen de Herrera (c.1562–c.1635) was a philosophically oriented kabbalist of Spanish origin. His Spanish writings, in Latin translation, were blamed for inspiring Spinoza’s views.

Moses Mendelssohn (1729–86), a leading figure of the European Enlightenment, spread Enlightenment ideas to Hebrew literature, fought for Jewish civil rights and did pioneering conceptual work on political theory, especially with regard to religious liberty in his Jerusalem. Solomon Maimon (1753/4–1800) took his name in honour of Moses Maimonides. Trained as a rabbi, he pursued secular and scientific learning and became an important and original critic of the philosophy of Kant. Nachman Krochmal (1785–1840), a leader of the Jewish Enlightenment in Galicia, found anticipations of Kant, Hegel and Schelling in the ancient Jewish writings. His work shows how a thinker whose underlying assumptions differ from those of the idealist philosophers could take their views in quite a different direction from the one they chose.

Hermann Cohen (1842–1918), a major Kantian philosopher and one of the first non-baptized Jews to hold an important academic post in Germany, applied his own distinctive version of critical idealism to the understanding of Judaism as a spiritual and ethical system. Franz Rosenzweig (1886–1929), an important Hegelian thinker, went on to formulate a Jewish existential philosophy that deeply influenced many of the most prominent Jewish thinkers of the twentieth century. Martin Buber (1878–1965), Zionist advocate of accommodation with the Palestinian Arabs and an admiring student of Hasidic traditions, added his own stamp to the continental tradition of Jewish philosophy by developing a widely influential dialogical philosophy that privileged relationships experientially and celebrated the I–thou, a mode of relation that allows for authentic encounter.

A number of twentieth century philosophers of Judaism have grasped at diverse threads of the Jewish experience, illustrating both the attractions of the tradition and the fragmentation produced by centuries of persecution that would culminate in the Holocaust, only to be accentuated by the centrifugal tendencies of Jewish life in post-Holocaust liberal societies. Ahad Ha’Am, the pen name of Asher Ginzberg (1856–1927), was an essayist who argued that the creation of a ‘spiritual centre’ of Jewish culture in Palestine would provide the sustenance needed to preserve the diaspora Jewry from the threat of assimilation.

David Baumgardt (1890–1963) was a philosopher who sought to reconcile ethical naturalism with the ideals he found in the Jewish sources, but, unlike Hermann Cohen, Baumgardt did not explore those sources in close detail. Mordecai Kaplan (1881–1981) sought to devise a social mission and communal identity for Jews without reliance on many of the core beliefs and practices that had shaped that identity in the past. Abraham Joshua Heschel (1907–72) sought to salvage the spiritual dimensions of Jewish experience, which found expression both in ritual and in ethical and social action.

Joseph Soloveitchik (1903–93) gave canonical expression to Orthodox ideals by focusing on the intellectual and ritual rigours of his archetypal figures, Halakhic man and the Lonely Man of Faith. Yeshayahu Leibowitz (1903–94), an influential Israeli thinker, struggled for the disengagement of authentic and committed religious observance from the toils of governmental officialdom. Jews are mandated, he argued, to observance, as a community. That imperative is not to be put aside. Neither can the observant pretend to ignore the State of Israel. But the State can give no mandate to religious observance, and religious faithfulness can impart none of its aura to the State. For it is essential not to place God in the service of politics. Emil Fackenheim (1916–) seeks an authentic response to the Holocaust, which he formulates in an intentionally inclusionary way, as a ‘614th’ commandment, not to hand Hitler a posthumous victory but to find some way, that might vary from individual to individual, of keeping alive Jewish ideas, practices and commitments.

Haredi theology: At the same time, Haredi Judaism has seen a resurgence of a systematic philosophical format for its beliefs. The founder of this system was Rabbi Eliyahu Eliezer Dessler, a student of the Kelm mussar yeshiva and later Mashgiach (spiritual supervisor) of Ponevezh yeshiva. Although never formally committing his ideas for publication, after his death in 1953 his students compiled and organized his numerous manuscripts in a five-volume work titled “Michtav Ma’Eliyahu”, later translated into English and published as “Strive for Truth”. His ideas have been popularized and promulgated by many Haredi educators. Notable among them are his student Rabbi Aryeh Carmel (main redactor of “Michtav Ma’Eliyahu”) and Rabbi Dr. Akiva Tatz (author of many works and a well known lecturer and activist in the kiruv (outreach) movement).

Haredim consider the fusion of religion and philosophy as difficult because classical philosophers start with no preconditions for which conclusions they must reach in their investigation, while classical religious believers have a set of religious principles of faith that they hold one must believe.

Some maintain, however, that in reality it is incorrect to direct this criticism solely at religious philosophy. Rabbi Eliyahu Eliezer Dessler (Strive for Truth Vol. 1) contends that no human being can possibly claim objectivity in philosophical investigations with moral implications: “..a person senses in advance that the answer will make a significant difference…On the solution will depend whether he will be obliged for the rest of his life to struggle with his baser desires…or whether he will be able to live without a higher responsibility”. On this basis Dessler maintains that only those who have spent years concentrating on the subjugation of their desires to their intellect, can even begin to claim intellectual impartiality. Indeed, according to this it is more likely for religious philosophy to succeed in attaining the truth then secular philosophy.

Some, however, hold that one cannot simultaneously be a philosopher and a true adherent of a revealed religion. In this view, all attempts at synthesis ultimately fail. For example, Rabbi Nachman of Breslov, seen as the most imaginative and poetic Hasidic mystic, views all philosophy as untrue and heretical. In this he represents one strand of Hasidic thought, with creative emphasis on the emotions. Approaching this point of view from the opposite direction, Baruch Spinoza, a pantheist, views revealed religion as inferior to philosophy, and thus saw traditional Jewish philosophy as an intellectual failure.

Others hold that a synthesis between the two is possible. One way to find a synthesis is to use philosophical arguments to prove that one’s religious principles are true. This is a common technique found in the writings of many religious traditions, including Judaism, Christianity and Islam, but this is not generally accepted as true philosophy by philosophers. One example of this approach is found in the writings of Lawrence Kelemen, in his Permission to Believe, (Feldheim 1990). A synthesis on a more profound level is seen in the works of the Hasidic leaders, who express an intellectual articulation of Hasidic thought, most notably in Habad, which seeks to bring Hasidism into complete intellectual analysis. On this they take a different view of mainstream philosophy to Rabbi Nachman of Breslov. In the writings of Habad, Hasidus is seen as able to unite all parts of Torah thought, from the schools of philosophy to mysticism, by uncovering the illminating Divine essence that permeates and transcends all approaches. One example of this is given by Schneur Zalman of Liadi in the early chapters of the Tanya. In a paranthetical side-column to the main text, the Kabbalists are said to agree with Maimonides’ description that “God is the knower, the knowledge, and the known”, but that this statement only applies to certain, stated Kabbalistic levels of Divinity, and no higher. For a fuller treatment of the nature and essence of Hasidic thought, and its relation to other disciplines in Judaism, see Hasidic philosophy.

Hasidic philosophy: Hasidic philosophy is the thought and teachings of the Hasidic movement founded by the Baal Shem Tov. It expressed the Kabbalistic tradition in a new paradigm in relation to man, and so could be conveyed to the Jewish masses. As the movement grew, it developed into various different interpretations, formed by the circles of close followers of the Baal Shem Tov, and his successor Dov Ber of Mezeritch. In the school of Chabad, formed by Schneur Zalman of Liadi, the mystical revivalism of the early Hasidic Masters was brought into a systematic philosophical articulation, that brought the esoteric Kabbalah of Isaac Luria into understanding. Interpreting the verse from Job, “from my flesh I see God”, Shneur Zalman explained the inner meaning, or “soul”, of the Jewish mystical tradition in intellectual form, by means of analogies drawn from the human realm. As explained and continued by the later leaders of Chabad, this enabled the human mind to grasp concepts of Godliness, and so enable the heart to feel the love and awe of God, emphasised by all the founders of hasidism, in an internal way. This development, the culminating level of the Jewish mystical tradition, in this way bridges philosophy and mysticism, by expressing the transcendent in human terms. See Hasidic philosophy for a more detailed treatment.

Holocaust theology: Judaism has traditionally taught that God is omnipotent (all powerful), omniscient (all knowing) and omnibenevolent (all good). Yet, these claims are in jarring contrast with the fact that there is much evil in the world. Perhaps the most difficult question that monotheists have confronted is “how can one reconcile the existence of this view of God with the existence of evil?” This is the problem of evil. Within all the monotheistic faiths many answers (theodicies) have been proposed. However, in light of the magnitude of evil seen in the Holocaust, many people have re-examined classical views on this subject. How can people still have any kind of faith after the Holocaust? This set of Jewish philosophies is discussed in the article on Holocaust theology.

Post-Enlightenment Jewish philosophers: Salomon Formstecher, Samson Raphael Hirsch (philosophy of Torah im Derech Eretz; belonged to the Neo-Orthodox movement of 19th century Germany, combating Reform Judaism. Orthodox Judaism philosophers: Eliezer Berkovits, Eliyahu Eliezer Dessler, Samson Raphael Hirsch, Abraham Isaac Kook, Emmanuel Levinas, Joseph Soloveitchik. Conservative Judaism philosophers: Bradley Shavit Artson, Elliot N. Dorff, Neil Gillman, Abraham Joshua Heschel, Max Kadushin, William E. Kaufman, Harold Kushner. Reform Judaism philosophers: Emil Fackenheim, Samuel Hirsch (belonging to Reform Judaism.)