Perhaps you’ve heard of Maimonides (Rabbi Moses ben Maimon, Rambam) and Nachmanides (Rabbi Moses ben Nachman, Ramban), two medieval scholars whose works are quoted frequently even today. You may not, however, have heard of Gersonides.

To Jewish scholars, Rabbi Levi ben Gershon is best known as the Ralbag, the author of Biblical and Talmudic commentaries, Jewish philosophy and Hebrew poetry. However, he is better-known to philosophers, scientists and mathematicians as Gersonides.

In the medieval era, science and philosophy were often categorized together. Thus Sefer Milhamot Hashem (The Wars of the Lord), Gersonides’ philosophical tractate (similar to Maimonides’ Guide for the Perplexed), also contains the author’s exploration into the scientific world.

While not all of Gersonides’ scientific works have been upheld by the test of time, many of his findings were far ahead of his times. For instance, Gersonides estimated stellar distances and refuted Ptolemy’s model of the solar system. He also worked with and refined scientific instruments such as the camera obscura and is credited with inventing the Jacob’s staff, a navigational instrument designed to measure the angular distance between celestial objects. Rabbi Levi’s Craters, a lunar geographical formation, honors Gersonides’ astronomical work.

Gersonides is also noted for his work in mathematics. His treatise Ma’aseh Choshev dealt with square roots, binomial coefficients and algebraic identities (and more).

Gersonides’ rational thought process, which is reflected in his scientific works, also shaped his philosophic ideas, which was shaped by Aristotelian philosophy. Like the philosophy of Maimonides (also an Aristotelian), Gersonides’ philosophy was criticized and rejected by many leaders in the Jewish community. However much they disagreed with his philosophy, his brilliance could not be denied and his commentaries remain popular to this day.

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