God is not able to be Perfectly defined, as one being measured according to the rules of Logic; because, α. He is not composed of Parts; for what is defined, as existing in the category of substance, is composed of a substantial genus and a form or substantial difference, characterized by which difference an Entity is differentiated from, and specific with respect to, its genus: but God is simple, free from composition. β. Neither does He admit a Univocal categorical Genus and a Specific Difference. For, whether you use the more remote Genus here, Being or Substance, or the closest Genus, Spirit, nothing from these creatures is univocally common with God, and so the Genus is not able to be called Univocal, which ought to agree equally with its species. But Theologians also observe that a Definition of God refuses a Specific Difference, because either the divine Attributes, or the Persons of the Trinity, are to be put in the place of the Specific Difference in the Definition. But neither in propriety of speech is able to obtain. Because being characterized a Difference an Entity is differentiated from, and specific with respect to, its genus. Now, a Being characterized by the divine Attributes is not diverse from Spirit or the spiritual Nature of God: neither are the former any more specific than the latter. They observe that for the same reason the divine Persons are not able to be considered as the Specific Difference in the Definition of God, because, if the distinct Persons were Specific Differences of the One divine Essence as Genus, they would be altogether the species of the divine Substance and as many substances as Persons, which is repugnant to the perfectly simple Unity of God; apart from the fact that it is not of one thing, unless it be one essential difference: compare ECKHARDUS, in his Fasciculo Controversiarum cum Calvino, chapter II, questions II, III, pages 30-37.
γ. And, therefore, God is not able to be defined perfectly, because He is not able to be comprehended perfectly.
 Heinrich Eckhard (1580-1624) was a German Lutheran Pastor and Theologian.