G-d’s unity means not only that there is but one Creator but that G-d is the only existing being. All of existence is absolutely nullified before Him and completely one with Him. Therefore, when one acts in defiance of G-d’s will as expressed in the commandments, he sets himself apart from G-d as though he were a separate and independent entity. This constitutes a denial of G-d’s unity, and the transgressor is therefore considered an idolator. This the Alter Rebbe now explains in detail.