Let me begin in a general way by talking about monotheism. As has been pointed out many times, monotheism is more than a numerical claim about God. In addition to asserting that there is only one God, it holds that this God is in some sense unique. Thus, Maimonides (GP 1.57, p. 133) maintains that to say that God is one is to say that God has no equal. We can understand “no equal” in either of two ways. The first is to follow the via negativa and argue that God bears no resemblance to anything else. God is neither a body, nor a force in a body, nor anything that resembles them. The second is to say that God exists necessarily and that everything else is dependent on God. In the beginning of the Mishneh Torah, Maimonides makes this point by saying that all beings other than God need God so that none would exist if God did not.

By the time he gets to the Guide of the Perplexed, Maimonides argues that the existence of a God with no equal and the creation of the world are the two pillars on which monotheism rests.