The Ralbag (Gersonides)

Rabbi Levi ben Gershon (1288–1344), known in the Torah world by the acronym Ralbag and in the scientific and philosophical world as Gersonides or Magister Leo Hebraeus, represents one of the high points of medieval Jewish rationalism.^{[1, 2]} His wide-ranging intellectual activity extended over many fields, from profound biblical exegesis and halakhic rulings, through daring metaphysical philosophy, to groundbreaking research in mathematics, astronomy and medicine.^{[1, 3]} The Ralbag was active in southern France, in the region of Provence, which served at that time as a central cultural crossroads where the exegetical traditions of northern France met the philosophy and science of Spain and the Muslim world.^{[4, 5]}

Historical Context and Intellectual Environment

The Ralbag spent his life in the cities of Orange, Avignon and Bagnols, under the relative protection of the papacy, which resided at that time in Avignon.^{[4, 5]} This environment gave him a certain degree of stability in a period in which other Jewish communities in France suffered from decrees and expulsions, such as the Shepherds' decree (the Pastoureaux) in 1320.^[5] The Ralbag's family was deeply rooted in the world of science; his father, Rabbi Gershon ben Shlomo, was a scholar who imparted to his son the foundations of secular studies alongside sacred studies.^{[4, 5]} 14th-century Provence was saturated with Hebrew translations of the writings of Aristotle, Averroes (Ibn Rushd) and Euclid, and the Ralbag became one of the important commentators on the writings of Averroes, writing on them "middle commentaries" that emphasize the depth of Aristotelian logic and metaphysics.^{[2, 6]}

Biographical Data and Stations of His Life

Milchamot Hashem: The Crowning Achievement of Rationalist Philosophy

The Ralbag's central philosophical work, "Sefer Milchamot Hashem," completed in 1329, is considered one of the most systematic and complex works ever written in Jewish thought.^{[7, 8]} The book is not merely religious apologetics, but a daring attempt to reconcile the contradictions between human reason, represented by Aristotelian philosophy, and the data of the Torah and revelation.^{[3, 7]} The Ralbag believed, with philosophical optimism, that the human intellect is capable of reaching a full understanding of the divine truths, and that the Torah and reason are two sources of one and the same truth.^[7]

The Structure of the Book "Milchamot Hashem"

The book is divided into six treatises, each devoted to a central metaphysical or cosmological question that occupied medieval thinkers ^{[8, 9]}:

• The first treatise: The immortality of the soul. The Ralbag discusses the nature of the soul and the possibility of intellectual immortality. He distinguishes between the "material intellect" (the intellectual potential) and the "acquired intellect," which is the sum of the intelligibles a person accumulates in his lifetime. Only the acquired intellect, composed of eternal truths, merits survival after death.^{[1, 7]}
• The second treatise: Foreknowledge of the future. An analysis of phenomena such as dreams, divination and prophecy. The Ralbag offers a naturalistic explanation according to which information about the future is transmitted from the Active Intellect to human beings with a suitable intellectual and imaginative preparation.^{[1, 7]}
• The third treatise: God's knowledge. One of the most disputed questions. The Ralbag argues that God knows things in terms of their general order and lawfulness, but does not know the contingent particulars arising from human free choice, since these are not in the category of a fixed "intelligible."^{[6, 10]}
• The fourth treatise: Providence. The Ralbag distinguishes between providence over the species (general) and individual providence. He argues that particular providence applies only to those individuals who have joined their intellect to the Active Intellect, and thereby they merit protection from the chance harms of nature.^{[1, 7]}
• The fifth treatise: The heavenly bodies. A comprehensive astronomical and physical study of the structure of the spheres, their movers and their relation to the Creator. This part is considered one of the important scientific works of the Middle Ages.^{[2, 7]}
• The sixth treatise: The creation of the world. A proof that the world was created in time out of a primordial formless matter and not as an absolute "something from nothing," in contrast to the position of Maimonides (Rambam).^{[2, 7]}

The Psychology and Metaphysics of the Soul

At the center of the Ralbag's teaching stands the belief that the purpose of man is intellectual knowledge.^[7] In his book he develops the doctrine of the "acquired intellect," which is the bridge between finite man and divine eternity.^[1] The human soul is not eternal by its very nature; it becomes so only when it acquires intelligibles – mathematical, logical and physical truths – which are part of the divine order of the universe.^{[1, 11]}

This process of the "intellectualization" of the soul is the key to true happiness. According to the Ralbag, a person who has not developed his intellect and has not acquired intelligibles – his soul dies with his body.^[1] This conception emphasizes the importance of education and scientific research not only as a practical tool, but as a supreme religious need for the salvation of the soul.^{[7, 12]} The Ralbag saw sciences such as mathematics and astronomy as a necessary preparation for attaining the higher intelligibles concerning God and the angels (the separate intellects).^{[2, 7]}

A Comparison of Positions: Ralbag versus Rambam

The Method of Biblical Exegesis: The "To'aliyot" as an Educational Tool

The Ralbag was a prolific commentator who wrote on most of the books of the Bible.^[6] His exegetical approach was characterized by a rigid and systematic methodological structure, which seeks to turn the reading of the Torah into a lesson in philosophy and leadership.^[5] He divided each chapter into three sections: "Explanation of the Words," "Explanation of the Matter" and "the To'aliyot" (lessons).^{[5, 13]}

The Methodology of the "To'aliyot"

The Ralbag's central innovation is the section of the "to'aliyot" (benefits, lessons), which appears at the end of each unit of study.^[5] The Ralbag believed that the Torah was written to benefit man on three main planes:

• To'aliyot in beliefs: clarifying truths of faith and philosophy hidden within the biblical narrative. For example, from the stories of Joseph he derives insights into the nature of dreams and into divine providence, which directs history for the good of all.^{[5, 14]}
• To'aliyot in character traits: moral guidance and social conduct. The Ralbag often emphasizes the importance of courtesy, of a dignified appearance before the authorities (as is learned from Joseph's change of clothes before he came to Pharaoh) and of brief and concise speech with kings.^{[5, 14]}
• To'aliyot in the commandments (halakha): the Ralbag seeks to show how the laws of halakha received from the Sages are anchored in the language of Scripture and in the laws of logic.^[5] In his commentary on the Torah, he devotes considerable space to the connection between the Written Torah and the Oral Torah, pointing to "roots" – basic principles of each commandment.^[5]

In his commentary on the Scroll of Ruth, for example, the Ralbag departs from the plain meaning of the verses in order to emphasize Ruth's legal status as a convert, deriving halakhic "to'aliyot" about the process of conversion and the need for a formal acceptance of the yoke of the commandments.^[6] In the Song of Songs, he sees a complex allegory of the encounter between the human intellect (the beloved woman) and the Active Intellect (the beloved), and quotes Aristotle dozens of times in order to clarify the philosophical concepts hidden in the language of love.^{[12, 13]}

The Scientist and Inventor: Astronomy and Mathematics

The Ralbag was not merely a theoretical thinker; he was an experimental scientist ahead of his time.^[2] He held that one should not rely on the authority of the ancients if his own observations showed otherwise.^[7] Astronomy for him was a "sacred science" through which one can come to know the greatness of the Creator and the wondrous order of the universe.^{[2, 7]}

Astronomical Achievements and Inventions

The Ralbag is considered one of the most important astronomers of medieval Europe.^[2] He invented instruments that changed the face of astronomical measurement:

• Jacob's staff (Baculus Jacobi): a simple but ingenious instrument for measuring the angles between stars and the height of the heavenly bodies above the horizon. The instrument consisted of a rod with perforated sliding plates, and it served sailors and astronomers for hundreds of years.^{[1, 2, 4]}
• The improved camera obscura: the Ralbag used a dark chamber in order to observe the diameter of the sun and the moon precisely, correcting the errors of his predecessors concerning the apparent changes in the size of the heavenly bodies.^{[1, 4]}
• Criticism of the Ptolemaic model: he cast doubt on Ptolemy's structure of epicycles (secondary circles), arguing that they do not fit the clear observations of the planets. His astronomical work was so highly esteemed that parts of it were translated into Latin by order of Pope Clement VI.^{[2, 4, 7]}

Mathematical Innovations and the Method of Induction

In his book "Ma'aseh Choshev" (1321), the Ralbag proved himself one of the most original mathematicians of the Middle Ages.^{[1, 15]} He was the first to use the method of mathematical induction explicitly and systematically.^{[1, 16]} He used this method to prove formulas in combinatorics, such as the number of possible combinations of a set of elements, as well as formulas for the sums of series.^{[1, 15]}

The book "Ma'aseh Choshev" is divided into two parts:

• A theoretical part: comprising 68 mathematical theorems proved in the Euclidean style, covering topics in arithmetic, algebra and number theory.^{[15, 17]}
• A practical part: comprising algorithms for performing complex arithmetical operations, extracting square and cube roots, and solving problems of ratios and proportions.^{[1, 15]}

Logic and Halakha: The Connection between Aristotle and Midrash

The Ralbag's contribution to the halakhic world is reflected in the work "Sha'arei Tzedek," attributed to him (although some dispute this because of differences in style).^[8] The book is a unique attempt to apply formal Aristotelian logic to the thirteen principles (middot) of Rabbi Yishmael by which the Torah is expounded.^[8] The Ralbag sought to show that halakhic inferences (such as kal va-chomer, the a fortiori argument, or binyan av, the generalization from a paradigm case) are not merely an exegetical tradition, but meet the criteria of rigorous formal logic.^{[5, 8]}

In his commentary on the Torah, especially on the books of Exodus and Leviticus, he applies these principles in order to derive laws directly from the verses of Scripture, at times proposing an original interpretation that differs from the accepted one, but always trying to reconcile it with the tradition of the Sages.^[5] He emphasized that the Torah cannot contain logical contradictions, and therefore every exegesis must be based on a firm rational structure.^[7]

Table of the Ralbag's Main Works

The Question of Astrology and Providence

Unlike Maimonides (Rambam), who rejected astrology as idolatry or as vanity, the Ralbag saw it as a legitimate natural science.^[1] He believed that the heavenly bodies are God's emissaries that govern the lower world (the earth) through physical forces that influence a person's temperament and fate.^[1] For the Ralbag, the configuration of the stars at the hour of birth largely determines the course of an individual's life and the fate of nations.^[1]

Nevertheless, the Ralbag was not an absolute determinist. He argued that God gave man the intellect, which enables him to rise above the decree of the stars.^[1] "The purposeful intellect" can remedy the harms that the stars have destined for a person. From this also follows his doctrine of providence: particular providence is not an arbitrary intervention of God, but the result of the development of the intellect, which enables a person to foresee natural dangers (arising from the configuration of the stars) and to be saved from them.^[1] In this way he made astrology part of a religious system that encourages intellectual effort and free choice.^{[1, 3]}

Criticism and Reception through the Generations

The Ralbag's teaching aroused a storm already in his lifetime and after his death.^{[7, 18]} His positions on the question of God's knowledge (that He does not know contingent particulars) and on the creation of the world (from primordial matter) were seen by many as too extreme and even as heresy.^{[6, 7]} Rabbi Chasdai Crescas and Rabbi Yitzhak Arama came out sharply against his positions, and one of his opponents called his book "Wars against the Lord."^{[7, 18]}

Despite this, his influence was enormous:

• In the Jewish world: his commentary on the Bible was included in the editions of "Mikraot Gedolot" alongside Rashi and Nahmanides (Ramban), which attests to a broad acceptance of his words in the field of exegesis.^[6] Later thinkers such as the "holy Shelah" and the Or ha-Chaim used his ideas in order to resolve the question of free choice.^[1]
• In the scientific world: his astronomical tables and instruments were used by Christian scholars and formed a basis for research in the Renaissance period.^{[2, 6]} A crater on the moon was named after him ("Rabbi Levi") in recognition of his contribution to astronomy.^[1]
• In modern philosophy: his ideas on the eternity of the intellect and on divine knowledge influenced Baruch Spinoza and Leibniz, who saw in him a model of a consistent rationalist attempting to understand God through the laws of nature and logic.^{[2, 11, 18]}

Summary and Conclusions

Rabbi Levi ben Gershon stands as one of the most original and courageous intellectuals in Jewish history.^{[2, 7]} He was not afraid to criticize the greatest of his predecessors and to propose radical solutions to existential questions, out of a burning faith in the power of the human intellect as a divine gift.^[7] His Torah teaching is not detached from his scientific research; for him, solving a mathematical equation, building an instrument for measuring the stars or interpreting a verse of the Torah are all aspects of the same religious service – the attainment of intelligibles and the binding of the soul to eternity.^{[7, 12]}

The Ralbag left behind a legacy of optimistic rationalism, teaching that the Torah and science are not enemies but partners in the human journey toward understanding the Creator.^{[3, 7]} Despite the criticism of some of his theological views, his work in the fields of exegesis, mathematics and astronomy ensures his place as a spiritual giant whose legacy continues to resonate in philosophical and scientific discourse to this day.^{[1, 6]}