An annotated critical edition of Mordekhai ben Eliezer Komtiyano`s Commentary on R. Abraham Ibn Ezra's Yesod Mora. Komtiyano was one of the leading Jewish philosophers in late medieval Byzantine. His commentary focuses on Ibn Ezra's statements regarding the reasons for the commandments, and raises many religious, scientific, linguistic and interpretive issues. Prof. Dov Schwartz's introduction deals with Byzantine commentaries on Ibn Ezra and with psychological and astrological aspects of Komtiyano`s commentary