Menachem Mendel Lefin (or Levin) was born in 1749 in Satanow, Podolia, in the region of present-day Ukraine. He received a traditional Jewish education and was introduced to the Jewish Enlightenment, or Haskalah, after meeting Moses Mendelssohn. Lefin believed, however, that it was possible to integrate traditional Judaism with secular study. He was a fierce opponent of chasidic thought and Kabbalah, or Jewish mysticism, preferring the rationalist approach of Maimonides. His writings included arguments against chasidism and in favor of studying natural sciences, and a translation of Maimonides’ Guide for the Perplexed into Rabbinic Hebrew. His most well-known work is Cheshbon HaNefesh, a guide to systematic introspection and self-improvement.