R. Levi b. Gershom (Ralbag, Gersonides)

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R. Levi b. Gershom, Gersonides
ר' לוי בן גרשום, רלב"ג
WorksBiblical commentaries, Milchamot Hashem, math, astronomy
Exegetical CharacteristicsRationalist, philosophical
Influenced byIbn Ezra, Rambam
Impacted onRan, Akeidat Yitzchak, Abarbanel



  • Name – 
    • Hebrew name – 
    • _ name – R. Levi b. Gershom
  • Dates – 1288 – 1344
  • Location – Provence
  • Education – 
  • Occupation – Torah scholar, philosopher, mathematician, and astronomer.1
  • Family – Ralbag came from a family of Torah scholars.2
  • Teachers – 
  • Contemporaries – 
  • Students – 
  • Time period – 
  • World outlook – 


  • Biblical commentaries – Ralbag wrote commentaries on Torah, Nevi'im Rishonim, and most of Ketuvim. These commentaries were completed between 1325 and 1338.3
  • Rabbinics – Ralbag writes in his introduction to Torah that he planned to write a Sefer HaMitzvot and a commentary on the Talmud,4 but no such commentary survived, and it is unclear whether he ever completed these works.5
  • Jewish thought and more – Ralbag wrote a philosophy work called Milchamot Hashem and astronomy charts called Luchot HaTekhunah. He also invented Jacob's Staff, a tool for measuring distances between celestial objects. In the field of mathematics, he wrote Ma'aseh Choshev (first edition 1321, second edition 1322), commentary on Euclid (early 1320s), De Sinibus, Chordis, et Arcubus,6 De Numeris Harmonicis,7 and others.
  • Misattributed works – 

Torah Commentary


Ralbag's commentaries on Bereshit, Shemot, Iyyov, and Kohelet follow a tripartite structure, in which he employs three modes of exegesis in interpreting each unit:8

  • Lexical definitions (Biur HaMilot).
  • Explanations of the storyline (Biur Divrei HaParashah).
  • Lessons derived from the story (Toalot). The Toalot are of three types: philosophical messages (deiot), morals (middot), and commandments (mitzvot). The Toalot dealing with the commandments contain shorashim (roots), which present the details of the mitzvah.

Most of Ralbag's other commentaries also contain Toalot,9 but they combine the lexical definitions and the explanations of the storyline into one section.10


Ralbag's rationalism impacts his understandings of many issues in Tanakh:

  • Angels – Ralbag does not believe in the concept of corporeal angels and therefore reinterprets the stories about angels in different ways:
    • Prophet – Bereshit 16:7, Bereshit 18:2, Bereshit 21:17, Bereshit 22:11, Bereshit 32:2, Shemot 14:1911, Shofetim 2:1, Shofetim 6:11-12, Shofetim 13:11-16.
    • Dream – Bereshit 21:17, Bemidbar 22:21-35, Shemuel II 24:16.
  • Miracles – Ralbag tries to minimize miracles as much as possible in two ways:
    • Dream, מראה הנבואה or allegory – Gan Eden (Bereshit 2:8), Yaakov's wrestling with the angel (Bereshit 32:25), Bilam and the donkey (Bemidbar 22:21-35).
    • דרך הטבע – creation (Bereshit 1:1), Noach's ark (Bereshit 6:15), pillars of fire and cloud (Shemot 14:24-29), Yam Suf (Shemot 14:21-22), land swallowing Korach (Bemidbar 16:28), Yehoshua's stopping of the sun (Yehoshua 10:12).

Use of Science and Realia



  • Verse by verse / Topical – 
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Textual Issues

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Significant Influences

  • Earlier Sources
    • Ibn Ezra – Ibn Ezra is quoted many times. In Bereshit 2:3, Ralbag thanks Ibn Ezra and the Rambam for explaining the creation of the world, and he says that, although their opinions were wrong, they guided him to the right track.
    • Rambam – the Rambam had the greatest influence of any figure on Ralbag. Ralbag cites him many times, usually in the philosophical portions of the commentary.
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  • Targum Onkelos – 
  • Rasag – 
  • R. Hai Gaon – 
  • R. Yona Ibn Janach – 
  • Rashi – Shemot 18:21
  • Ralbag's grandfather, R. Levi HaCohen – Shemot Beiut HaMilot 34:9.
  • Ralbag's father, R. Gershom – Bereshit Beiur HaMilot 24:23, 40:14-15, 42:11-16, 44:10, 49:10, Shemot Beiur HaMilot 17:16, Vayikra 18:28-30.
  • Greek philosophers – Bereshit 1:28 shoresh 3 (Plato)

Unattributed Influences

  • Raavad – In Bereshit 48:4-5 and Bemidbar 26:54-55, there appears to be direct influence of the Raavad (cited in Shitah Mekubetzet Bava Batra 117b.)
  • Ramban – Ralbag never cites Ramban explicitly, although he sometimes explains exactly like Ramban, and sometimes seems to be reacting against him. Some have suggested12 that Ralbag didn't like Ramban since his exegeses was too mystical, but that he didn't want to confront him explicitly.


Later exegetes

Ralbag's works met with a mixed reception. Some admired his commentary and works, while others boycotted them and called his Milchamot Hashem (Battles of Hashem) Milchamot im Hashem (Battles with Hashem).13 Ralbag's positions had an influence on several subsequent commentators from Christian Spain:

  • Ran – 
  • Akeidat Yitzhak – 
  • Abarbanel –