Yihud Hashem, the Belief in the Absolute Unity of God, is the second of Rambam’s positive commandments. Along with the requirement to believe (or know) that there is a First Cause, this mitsvah occupies the bulk of the first chapter of Rambam’s Mishneh Torah, and will be our focus this week. Not surprisingly, Rambam gives the end of the verse of the Shema as the source of this commandment—Hashem elokenu Hashem ehad is not only a statement of fact, it is a positive commandment to believe.

Rambam’s definition of ehad, oneness, goes beyond what we might think at the most literal level. Raised (most of us) in largely Christian societies, we might have become accustomed to accepting oneness as a denial of multiple gods, such as the Trinity. That statement of oneness, however, would only assert God’s uniqueness, whereas Rambam sees it as declaring (and commanding a belief) that God has no parts or constituent units. God is an Absolute Unity, with no divisions in that Oneness.

In addition, or perhaps as a corollary, God has no limits or end, which necessarily means that He has no body (since a body, by definition, has an end-point). To those who know of the work Shiur Qoma, a book already well-known in Rambam’s time that describes God in directly physical terms and measurements (although ones that are orders of magnitude greater than any creature on earth), Rambam’s view achieves even greater interest. It was not only that he was denying the possibility that idols actually represent God; he was denying the existence of any physical component to God, since that would limit Him, and His Unity.

God’s not having a body creates a problem for human beings in their attempts to relate to Him (aside from the pronoun issues, which are completely unsolvable). Since all we know is a physical existence, in which everything that is has some physical aspect, we are unable to develop a meaningful conception of a non-physical Being. This problem (for us) is captured (for Rambam) in the verse (Yeshaya 40;25), "ve-el mi tedamyuni ve-eshveh, to whom can you compare Me and I will be comparable."

At the simplest level, the verse denies the feasibility of idolatry, since none of the other gods are as powerful as the True God. Rambam’s citing the verse in our context adds another element, the recognition that human beings do not possess any meaningful way to characterize God. At the base level, that means that, despite the world being full of His glory (as the verse says), God is so distinctly Other that we cannot actually grasp that glory in significant ways.

This aspect of God becomes important in many other contexts, where Rambam would caution us to keep in mind that we cannot make any accurate statements about God. God does not speak in the way we might think of, or act, or anything; all expressions about Godare simply concessions to the needs of human vocabulary. Indeed, Rambam spends the bulk of the first section of his Moreh Nevukhim dealing with terms in Tanakh that might seem to indicate a physical aspect or occurrence in relationship to God, and showing the meaning of those texts in a way that alleviates the problem.

One specific example of the challenge of God comes in the context of Moshe Rabbenu’s request (on Mount Sinai, after the Sin of the Golden Calf) har’eni na et kevodekha, show Me your glory. Rambam separates this request from that of hodi`eni na et derakhekha; the latter is a request for insight into the standards lf justice and kindness that characterize this world, information that is in fact much more accessible to humans than the first request. Kavod, however, Rambam takes to mean something much more essential to the focus of the request, and his explanation of it reveals some of the challenges he saw in our attempts to get to "know" God.

To prepare for Rambam’s explanation, we should pause for a moment to consider what we mean by "knowing" someone. One meaning of the word is that we can recognize that person, can distinguish him or her from others, even those with perhaps similar faces. In Rambam’s view, that knowledge indicates that there is a separate space in our intellects accorded to that person. (I will not enter now into a discussion of the science of how people know things; if Rambam meant that every piece of knowledge has its own cell in the brain, current science probably disagrees. To the extent that he only meant that each person has some unique hold in our minds, if only in the particular grouping of characteristics that codes for the person’s name, it accords just fine with current neuroscience). Moshe Rabbenu, Rambam claims, was trying to attain such knowledge of God that he could develop a similar space in his brain for God as for any other friend.

That’s actually a pretty subtle reading of the text. Moshe was not asking to know God physically, since there is no such thing. If so, what would it mean to know God? For Rambam, it would mean that we could code "God" in our brain in such a way that it is as well-defined, and as accessible to our experience, as any other person we know.

God’s response then also makes a great deal of sense—humans cannot achieve such a knowledge of God, but He can vouchsafe Moshe the kind of knowledge (meaning the kind of mental identification experience) as if someone knew the back of someone else’s head, but not the front. It is possible, after all, to know someone from behind without ever seeing the person’s face, but that is not as deep a knowledge of the person as seeing him or her from the front. Moshe Rabbenu’s brain was able to grasp God as fully as the latter standard, but not the former.

Sefer haHinukh stresses that denying this unity is a denial of the Faith as a whole, and that any mitsvot such a person performs are meaningless. He, of course, was writing in a Christian context, where there was pressure to convert, but the message that our observance of mitsvot must be in response to the command of the Creator as defined by Judaism—one who is absolutely unified—is timeless and universal. Shabbat Shalom.