LEVI BEN GERSHOM

LEVI BEN GERSHOM (1288–1344; acronym: RaLBaG ; also called Maestre Leo de Bagnols; Magister Leo Hebraeus; Gersonides ), mathematician, astronomer, philosopher, and biblical commentator, born probably at Bagnols-sur-Cèze (Languedoc – now département du Gard, France). He lived primarily in Orange and briefly at Avignon. Little is known about his life beyond the fact that he maintained relations with important Christian persons. Levi had very broad intellectual interests and contributed to many areas of human learning.

Scientific Work

The scientific works of Levi deal with arithmetic, geometry, trigonometry, and astronomy.

His first work, written in 1321, the Sefer Ma'aseh Ḥoshev or Sefer ha-Mispar ("The Book of the Number"; published with a translation in German by G. Lange, 1909), is divided into two parts: principles and applications. The work deals with addition, subtraction, multiplication, series, permutation, combination, division, extraction of roots, and proportion. In 1343, Levi composed a second book on arithmetic for Philip of Vitry, bishop of Meaux. Only the Latin translation of the book has been preserved, under the title De numeris harmonicis (published by J. Carlebach, Lewi ben Gerson als Mathematiker (1910), 129–44).

In his commentary on Books 1–5 of Euclid, which resembles his commentaries on *Averroes, Levi attempts to construct a geometry without axioms, but, in place of Euclid's axioms, he unwittingly introduces other axioms of his own.

In his important treatise on trigonometry (translated into Latin in 1342 under the title De sinibus, chordis et arcibus and dedicated to Pope Clement vi), Levi rediscovered independently the sine theorem in the case of plane triangles (proportionality of sines to opposite sides); his sine tables are correct to the fifth decimal.

Talmudic and Liturgical Works

A commentary on the 13 hermeneutical rules of R. *Ishmael (printed in Jacob Faitusi, Sefer Berit Ya'akov, 1800) has been attributed to Levi as well as a commentary on the aggadot of Bava Batra, titled Meḥokek Ẓafun. This attribution is probably erroneous. In his commentary on the Pentateuch, Levi reports that he wrote a commentary on the talmudic treatise Berakhot, but this commentary is lost. An eminent talmudist, Levi was consulted on questions of halakhah (see rej, 44 (1902), 82–86). A responsum of his can be found in the She'elot u-Teshuvot of Isaac de Lattes (1860). Three poems (pizmonim) for the holiday of Shavuot and a viddui (confession of sins) composed by Levi were published and translated into French by C. Touati (rej, 117 (1958), 97–105). Levi is also the author of a parody written for the festival of Purim, titled Megillat Setarim ("Scroll of Mysteries").

Commentaries on Aristotle and Averroes

In one of his first philosophical works, Sefer ha-Hekkesh ha-Yashar (1319), translated into Latin under the title Liber syllogismi recti, Levi corrects certain inaccurate arguments of *Aristotle in his Posterior Analytics. Levi became acquainted with Aristotle's views by reading the paraphrases and commentaries of Averroes, and he himself wrote supercommentaries on a number of them: on the paraphrase of the Physics (1321), on the middle commentary of the Physics (1321), on the paraphrase of the De generatione et corruptione (1321), on the paraphrase of the De caelo (1321), on the paraphrase of the Meterologica (1321), on the middle commentary of the Organon (1323), on the paraphrase of the De animalibus (1323), on the paraphrase of the De anima (1323), on the paraphrase of the Parva naturalia (1324), on two questions of Averroes concerning Aristotelian logic, and on the letters concerning the union of the separate intellect with man. The supercommentaries on the middle commentary of the Metaphysics and the De plantibus have been lost. The supercommentaries of Levi on Averroes exist only in manuscript. The Latin translation by Jacob *Mantino of one section of the supercommentary on the Organon was published in volume one of the Venice edition of the works of Aristotle (1550–52).

In his commentaries on Averroes, which are important for understanding his philosophy, Levi paraphrases the text but frequently inserts notes of varying lengths, preceded by the words: amar Levi ("Levi says"). In these notes he develops, criticizes, or corrects aspects of the ideas of Aristotle or Averroes. He manifests an independent spirit in relation to the two philosophers. Several passages from commentaries on Averroes appear in H.A. Wolfson, Crescas' Critique of Aristotle (1929).

Biblical Commentaries

Levi wrote commentaries on Job (1325), Song of Songs (1325 or 1326), Ecclesiastes (1328), Ruth (1329), Esther (1329), the Pentateuch (1329–38), the Former Prophets (1338), Proverbs, Daniel, Nehemiah, and Chronicles (1338). All of these were published, some in several editions. The commentary on Job is one of the first books to be printed in Hebrew (Ferrara, 1477).

The biblical commentaries of Levi are the work of an exegete and a philosopher. Certain of his literal explanations are still of interest today. Diverse questions of a philosophical or theological nature are discussed by him, such as the problem of providence, miracles, and the Messiah. From each book of the Bible, Levi extracts the ethical, philosophical, and religious teachings that may be gleaned from the text and calls them to'alot or to'aliyyot. A collection of these to'aliyyot was printed separately (Riva di Trento, 1570). In his voluminous commentary on the Pentateuch, Levi attempts to reconstitute the halakhah rationally, basing himself on nine logical principles which he substitutes for the traditional 13 *hermeneutical rules, and condemning allegorical interpretations. In the 15^th century in Italy, Judah Messer *Leon wanted to prohibit the study of Gersonides' commentary on the Pentateuch, using the pretext that the latter wished to fabricate a new Talmud.

Sefer Milḥamot Adonai

Levi's major work, to which he constantly refers in his commentaries on Averroes and the Bible, is the Sefer Milḥamot Adonai ("The Book of the Wars of the Lord"), begun in about 1317 and completed in 1329. In this work, he treats problems which, in his opinion, have not received a satisfactory solution by preceding philosophers, including *Maimonides. Divided into six parts, the work deals with the immortality of the soul (first book), dream, divination, and prophecy (second book), divine knowledge (third book), providence (fourth book), celestial spheres, separate intellects and their relationship with God (fifth book), the creation of the world, miracles, and the criteria by which one recognizes the true prophet (sixth book). Numerous manuscripts of the Milḥamot are extant, but the book was printed only twice, and then imperfectly (Riva di Trento, 1560 and Leipzig, 1863). The first four books of the Milhamot were translated into German with notes by B. Kellerman (Die Kaempfe Gottes, 2 vols., 1914–16), but this translation is unreliable. A French translation of books three and four, based on a critical edition together with an introduction and notes, was made by C. Touati (1968).

The Milḥamot is written in a precise and technical Hebrew but, like Levi's other works, it is characterized by repetitiveness. In almost all the questions analyzed, Levi quotes the opinions of his predecessors – Aristotle, *Alexander of Aphrodisias, *Themistius, Al-*Farābī, *Avicenna – with whom he became acquainted largely by reading Averroes, as well as the opinions of Averroes himself and of Maimonides. He enumerates the arguments that, respectively, support and disprove their theses and, finally, he expounds his own theory. Though lacking a systematic structure, the Milḥamot contains an almost complete system of philosophy and theology. However, this work cannot be understood unless one is familiar with Levi's commentaries on Averroes and the Bible, which explain and complement the Milḥamot on many points. In order to understand the ideas of Levi, one should have recourse to all his philosophical and exegetic works.

His Philosophy

god

Demonstrating the existence of God, Levi rejects the proof, favored by many of his Aristotelian predecessors, according to which the existence of God, as prime mover, can be derived from the various motions existing in the world. In its place he presents a proof based on the orderly processes existing in the world, that is, an argument from design. According to this proof, the observed regularity of processes of generation within the sublunar world leads to the conclusion that these processes are produced by an intelligence. This intelligence is the so-called agent intellect (see *Intellect) which governs the sublunar world. This intelligence endows matter with its various forms and is aware of the order it produces. The activities of the agent intellect are mediated by the natural heat which is found in the seeds and sperms of plants and animals and this natural heat in turn is produced by the motions of the various celestial spheres. Since these motions contribute to the perfection of the terrestrial world, they must also be produced by intelligences which know them, that is, they are produced by the intelligences of the celestial spheres. From what has been said, it can be seen that the celestial and terrestrial worlds form an ordered, unitary whole and this requires that there exists a supreme being which produces and knows this order. This being is God.

Unlike Maimonides, Levi maintains that it is possible to ascribe positive attributes to God without reducing or changing His absolute unity and simplicity. Admitting that real multiplicity exists only in beings composed of form and matter, he argues that all the predicates of a proposition dealing with a non-material entity are derived analytically from the subject. According to Levi these predicates are simply an explanation of the subject and introduce no plurality whatever. Opposing Maimonides' doctrine of negative attributes, Levi teaches that man may have a certain positive knowledge of God, based on the observation of His actions. The essential action of God is thinking, and, consequently, the effusion of all forms. All the attributes that man recognizes in his own form are just so many attributes of God. Since the attributes common to both man and God have the relation of cause and effect, it is impossible to consider them absolute homonyms, that is, terms which have nothing in common except their names.

By means of a knowledge that is neither temporal nor changing, God eternally perceives the general law of the universe, that is, those laws governing the movements of the heavenly bodies and, through them, the sublunar beings. God is aware of the fate that awaits all individuals, inasmuch as they are distributed in groups subject to the same celestial determinism which, in principle, governs all the conditions of man. However, this determinism, essentially beneficial, may occasionally cause misfortune. God has therefore accorded man freedom which allows him to liberate himself from the shackles of determinism. An individual who makes use of his freedom is no longer subject to the universal law known by God; he has accomplished an act which is absolutely undetermined and which remains totally unknown to God. God's knowledge, however, does not undergo any modification; it always remains true, since the author of the free act is no longer included in the necessary and universal proposition thought by God. For Levi, God's knowledge embraces all the events of this world, with the exception of free acts that cannot be predicted by any type of knowledge. Levi is convinced that he has finally succeeded in reconciling two contradictory fundamental principles of the Bible: divine omniscience and the freedom of man's will.

The providence of God extends a means of protection that increases in proportion to man's moral and intellectual perfection. Through the determined activities of the stars, God assures a maximum of good to men in general and spares them a maximum of ills. Premonitions, dreams, prophecies and the exercise of free choice save certain individuals from harmful effects of determinism. However, the existence of evil cannot be denied since, at times, the righteous do suffer. But Levi upholds the belief that the true good which is specifically human is the immortality of the soul, and it is this immortality, rigorously proportioned according to one's moral rectitude and intellectual perfection, that constitutes the actual recompense of God.

creation of the world

In opposition to Maimonides who held that the creation of the world cannot be demonstrated philosophically, Levi offers philosophic arguments designed to show that the world came into being. One such argument is that everything produced by a final cause, ordained toa certain end, and serving as a substratum for accidents, cannot exist eternally. Since the world fulfills all these conditions it follows that it cannot be eternal, that is, that it has a beginning in time. He derives the same conclusion from the state of the sciences. Were the world eternal, he argues, the sciences would be more advanced than they are. He holds further thata large number of Aristotle's arguments designed to prove the eternity of the world beg the question. They are based on the assumption that the physical laws discovered within the world are also applicable to its beginning. However, this assumption is fallacious. For while it is true that there are some similarities between processes within the world and creation (Levi here is more moderate than Maimonides who holds a similar view), creation is also unique. Whereas motions in the world take place in time, creation occurred in an instant. However, since nothing can be created out of nothing, the world has a substratum, an eternal body which is nonetheless a relative non-being, in the sense that it possesses no form whatever. This substratum has no "existence" in the proper sense of the word, since all existence derives from form. Thus the theological difficulty that might give rise to the possibility of more than one eternal being is avoided.

man

God has arranged the universe so that man, the most perfect being of the sublunar world, is accorded the greatest good and is spared the greatest amount of ills possible, as we have already seen. Revelations of different types protect him (premonitions, dreams, etc.). His imagination, under the action of one or several celestial bodies, envisions the menace that certain stellar configurations may place upon him. God has equally furnished man with a practical intellect, from which he learns the indispensable arts of self-preservation, and a speculative intellect which permits him to perceive truth and to achieve immortality. The material or potential intellect is not a substance but rather a simple disposition, whose substratum is the imagination. Building on the sensations, the human intellect abstracts concepts; but sensation is only an incidental agent in the production of knowledge, for knowledge in its true sense is the comprehension of intelligibles as they exist in the agent intellect. The human intellect, having understood the intelligible, which is eternal, becomes itself immortal. Differing from Averroes, who maintained that, at this state, the human intellect loses its individuality, Levi held that immortality is individual.

israel

Providence extends particularly to the children of Israel, chosen by God through His covenant with the Patriarchs. Prophecy is a kind of revelation that is superior to all other types of revelation, and differs from them not in degree but in nature. The prophet must necessarily be a preeminent philosopher who grasps the general laws governing changes in the sublunar world as they exist in the agent intellect. By means of his imagination, he applies this knowledge to given individual or communal situations, announcing the good or evil events that may befall a person, a group, or an entire people, as a result of the operation of the laws of nature. He is also capable of predicting a miracle, which is a violation of nature, not, as Maimonides thought, an event included in the laws of nature at the time of the creation of the world. Levi maintains that a miracle is produced at a particular time and place, and that it occurs when the agent intellect suspends normal, natural law, since it no longer applies to certain circumstances. Though miracles are not part of the laws of nature, or subject to them, they have their own laws. However, since a miracle is produced by the agent intellect, which can only act upon the sublunar world, no miracles can occur in the translunar world. Thus, for example, the sun did not really stand at the order of Joshua; the victory at Gibeon was attained during the short lapse of time when the sun seemingly stood at its zenith.

Through the intermediacy of Moses, the greatest of all prophets, God gave Israel the Torah, which, through its mitzvot and speculative truths, aims to help the children of Israel attain the moral and intellectual perfection which makes immortality possible for them. The commandments have various purposes, which Levi expounds in detail, but the purpose of most of them is to remove materialistic tendencies and teach the existence of forms. Finally, the Torah has revealed certain metaphysical truths that the philosophers have never been able to deduce, namely, the creation of the world and the immortality of the soul.

eschatology

Levi's eschatology is based on a tradition that there are two Messiahs. After the Messiah son of Joseph dies, having been assassinated, the Messiah son of David will appear. He will be greater than Moses, not because he will promulgate a new Torah, but because he will accomplish a miracle greater than those of Moses: the resurrection of the dead, an event which will convert all peoples of the earth to the true religion. He predicts the coming of the Messiah for the year 1358. During messianic times, the world will follow its usual pattern, men will die as before, but the earth will be filled with knowledge of God and human liberty will be utilized for good ends.

Views on Levi ben Gershom

On account of his boldness and of the suspicion of heresy fastened to him, Levi was subject to virulent attacks. Certain of his doctrines became the object of harsh criticism on the part of Ḥasdai *Crescas. Abraham *Shalom, while defending him against Crescas, censured him for other reasons. Shem Tov *Ibn Shem Tov labeled Levi's major work the "Wars against the Lord." *Isaac b. Sheshet Perfet, though recognizing Levi as a great talmudist, maintains that it is prohibited to accept certain of his theories. Isaac *Abrabanel, in several of his works, also criticizes him. However, even the most vehement critics of Levi, who very often did not understand his real thought, did not hesitate to borrow some of his ideas. His influence continued to exert itself even as late as the 19^th century, when he is mentioned in *Malbim's commentary on Job.

[Charles Touati]

As Astronomer

Milḥamot Adonai contains an astronomical treatise of 136 chapters. This astronomical section (Book v, Part 1) is not included in the manuscripts or printed versions of the rest of the work, but it was translated in its entirety into Latin. There also exists a second Latin version of the first few chapters dedicated to Pope Clement vi. The text covers most of the topics of medieval astronomy: trigonometry (the construction of the sine table and the solution of triangles); the construction and use of various astronomical instruments; an analysis of several schemes for arranging celestial motions; a discussion of solar, lunar, and planetary motions including tables to aid in their computation; and a discussion of the order of the planets and their distances from the earth.

The astronomical treatise was not meant to be an elementary text for students, but presupposes some familiarity with medieval astronomical literature. Although the work is clearly in the Ptolemaic tradition, Levi deals quite critically with his sources and often rejects earlier views in favor of his own. His most important innovation in terms of technical astronomy was his new geometrical model to account for lunar motion, which he describes in chapter 71. He argues that his new model corrects a glaring fault of Ptolemy's lunar model, which brought the moon so close to the earth at quadrature that it appeared twice as large as its observed size. Levi considered agreement with his own observations to be the principal criterion in choosing between alternative models for the motions of the celestial bodies; in this he departed from the widespread medieval dependence on the observations recorded in Ptolemy's Almagest. In addition to Ptolemy, Levi relied on al-Battānī, the famous ninth-century Arab astronomer, and to a lesser extent on Abraham *Ibn Ezra and *Abraham bar Ḥiyya. Levi carefully described his observations of four solar and six lunar eclipses, as well as observations of the moon and of the planets under different conditions. Such extensive recording of observations were quite rare among medieval astronomers.

Levi's best-known contribution to astronomy is his invention of the Jacob Staff, which was widely used to measure the angular separation between two celestial bodies. This instrument became an important navigational tool and was especially popular in the 16^th century among European sailors.

Most medieval scholars accepted the order of the planets presented by Ptolemy in The Planetary Hypotheses: Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn, and the fixed stars. There was, however, some dispute concerning the place of the sun in relation to Mercury and Venus. Levi considered several possibilities in detail, but seems to have preferred the theory that the sun lies below both planets. In another departure from Ptolemy, who set the distance to the fixed stars at 20,000 earth radii, Levi argued that those stars are more than 159 × 10¹² earth radii away, a truly astounding distance in terms of medieval science.

[Bernard R. Goldstein]

add. bibliography:

S. Feldman, The Wars of the Lord, vol. 3 (1999), 520–32; M. Kellner, "Bibliographia Gersonidiana: An Annotated List of the Writings by and about R. Levi ben Gershom," in: G. Freudenthal (ed.), Studies in Gersonides – A Fourteenth-Century Philosopher-Scientist (1992), 367–416; C. Sirat, S. Klein-Braslavy, and O. Weijers, Les methodes de travail de Gersonide et le manierement du savoir chez les scolastiques (2003), 357–76. general literature: G. Dahan (ed.), Gersonide en son temps (1991); H. Davidson, "Gersonides on the Material and Active Intellects," in: G. Freudenthal, Studies in Gersonides – A Fourteenth-Century Philosopher-Scientist (1992), 195–265; S. Feldman, "Gersonides' Proofs for Creation of the Universe," in: paajr, 35 (1967), 113–37; idem, "Platonic Themes in Gersonides' Cosmology," in: Salo W. Baron Jubilee Volume (1975), 383–405; idem, "Gersonides on the Possibility of Conjunction with the Agent Intellect," in: Association for Jewish Studies Review, 3 (1978), 99–120; G. Freudenthal, "Human Felicity and Astronomy – Gersonides' Revolt Against Ptolemy," in: Da'at, 22 (1989), 55–72; idem, Gersonide: Genie Solitaire," in: Sirat, Braslavy-Klein, and Weijers, 291–316; R. Glasner, "The Early Stages in the Evolution of Gersonides' Wars of the Lord," in: jqr, 87 (1996), 1–47; B. Goldstein, The Astronomy of Levi ben Gerson (1985); idem, "Preliminary Remarks on Levi ben Gerson's Contributions to Astronomy," in: The Israel Academy of Sciences and the Humanities, 3:9 (1969), 239–54; A. Ivry, "Gersonides and Averroes on the Intellect: The Evidence of the Supercommentary on the De Anima," in: G. Dahan (ed.), Gersonides en son temps (1991), 235–51; M. Kellner, "Gersonides on Miracles, the Messiah and Resurrection," in: Da'at, 4 (1980), 5–34; idem, "Gersonides on the Problem of Volitional Creation," in: huca, 51 (1980), 111–28; idem, Gersonides' Commentary on Song of Songs (1998); S. Klein-Braslavy, "Gersonides on Determinism, Possibility, Choice and Foreknowledge," in: Da'at, 22 (1989), 5–53 (Heb.); idem, "Prophecy, Clairvoyance and Dreams and the Concept of "Hitbodedut" in Gersonides' Thought," in: Da'at, 39 (1997), 23–68; T. Langermann, "Gersonides on Astrology," Appendix to vol. 3 of The Wars of the Lord, 506–19; idem, "Gersonides on the Magnet and the Heat of the Sun," in: Freudenthal (ed.), Studies on Gersonides, 276–82; J. Levi, Commentaries of Ralbag on the Torah, 5 vols. (1992, 1994, 1997, 1998, and 2000); C. Manekin, "Gersonides' Logical Writings: Preliminary Observations," in: paajr, 52 (1985), 85–113.