Phenomenology of Spirit, Preface, paragraph 25

That the true is real only as system, or that substance is essentially subject, is expressed in the notion which represents the absolute as spirit, which is the grandest concept of all, and which pertains to modern times and its religion. Spirit alone is real; it is the essence, or being-in-itself, the acting and determining, the being-other and being-for-itself, and, in this determination or being-outside-of-itself, remains in itself; or, it is in and for itself. This being-in-and-for-itself, however, is only for us or in itself, it is the spiritual substance. It has to become for itself, it must be knowledge of the spiritual and knowledge of itself as spirit, which means, it must be an object to itself, but, just as immediately, cancelled object, reflected into itself. It is for itself for us only to the degree that its spiritual content is produced by itself; to the degree that, for itself, it is for itself, then this self-production, the pure concept, is at the same time the objective element in which it has its existence, and in this manner it is object reflected-in-itself for itself, in its existence. Spirit, which knows itself to be spirit thus developed, is science. It is its reality, and the kingdom it erects for itself in its own native element.