Ancient Kabbalists {refer to} "Echod, Yochid, Myuchod", "Unique One, Particular One, Individual One."
"Echod" signifies that the Creator is equally present everywhere in all worlds. "Yochid" signifies that everything is drawn from Him, and although before us there appears a multiplicity of abundance, in Him, in the Source all is unity, even as His Substance itself. All abundance springs from the One Origin in which no differences are discernible. Thus, Heavenly Abundance as Its Source, cannot be defined. "Myuchod" signifies that although in Creation manifold deeds are executed, the One Power performs all. Finally, these manifold actions revert to the Unique Phases which engulfs them into Its Unity... The same thought is also expressed by Maimonides (Rambam) in the words: "He knows, He is that Which is known, and he is Knowledge."
(pp. 28-29)
There is no single substance existing in the world, whether it be that which we experience through the senses, or that which we perceive through the mind, which is not comprised in the Creator. Everything emanates from Him. Therefore, what we know as contrary, or unrelated in Him, are but one unified Substance.
(p. 28)