As the one notion is the common principle underlying all logic, there appear in the development of Essence the same attributes or terms as in the development of Being, but in a reflex form. Instead of Being and Nought we have now the forms of Positive and Negative; the former at first as Identity corresponding to pure and uncontrasted Being, the latter developed (showing in itself) as Difference. So also, we have Becoming represented by the Ground of determinate Being: which itself, when reflected upon the Ground, is Existence. The theory of Essence is the most difficult branch of Logic. It includes the categories of metaphysic and of the sciences in general. These are products of reflective understanding, which, while it assumes the differences to possess a footing of their own, and at the same time also expressly affirms their relativity, still combines the two statements, side by side, or one after the other, by an 'Also,' without bringing these thoughts into one, or unifying them into the notion. A.--ESSENCE AS GROUND OF EXISTENCE. (a) _The pure principles or categories of Reflection._ (α) Identity. 115.] The Essence lights up _in itself_ or is mere reflection: and therefore is only self-relation, not as immediate but as reflected. And that reflex relation is self-Identity. This Identity becomes an Identity in form only, or of the understanding, if it be held hard and fast, quite aloof from difference. Or, rather, abstraction is the imposition of this Identity of form, the transformation of something inherently concrete into this form of elementary simplicity. And this may be done in two ways. Either we may neglect a part of the multiple features which are found in the concrete thing (by what is called analysis) and select only one of them; or, neglecting their variety, we may concentrate the multiple characters into one. If we associate Identity with the Absolute, making the Absolute the subject of a proposition, we get: The Absolute is what is identical with itself. However true this proposition may be, it is doubtful whether it be meant in its truth: and therefore it is at least imperfect in the expression. For it is left undecided, whether it means the abstract Identity of understanding,--abstract, that is, because contrasted with the other characteristics of Essence, or the Identity which is inherently concrete. In the latter case, as will be seen, true Identity is first discoverable in the Ground, and, with a higher truth, in the Notion.--Even the word Absolute is often used to mean no more than 'abstract.' Absolute space and absolute time, for example, is another way of saying abstract space and abstract time.