User blog comment:The Nooby Assassin/Altair religion/@comment-4043223-20120131034837

As far as I know the Assassins are athiests (in the AC universe) and it is likely that Altair is the same. During his many years of looking into the Apple he began to question the belief system of many of the current day (3rd crusade era) people and the conflict it brought about. For more info you should check out the Assassins article and the Codex article.