There is no "official" Mitzvah requiring one to believe in the 13 Principles of Emunah of the Rambam. If this is true, how can the Rambam say that a Mitzvah-keeping Jew—who does not believe in these 13 principles—is actually an Apikores!? In this new FUNDAMENTALS series, Rabbi Stark takes a deep dive into the significance of the Rambam’s Yud Gimmel Ikrei Emunah.