The individual circle thus ruptures itself because it is in itself a totality, it breaks through the limit of its own elements and establishes another sphere. The whole presents itself then as a circle of circles in which each circle is a necessary moment, so that the system of its characteristic elements constitutes the whole idea, which also appears in each individual part (p. 51)
Now since the idea is reason identical to itself, which, in order to be for itself stands in opposition to itself and is itself an other, but in this other is identical to itself, science falls into three parts: (1) logic, the science of the idea in and for itself; (2) the philosophy of nature, as the science of the idea in its otherness; (3) the philosophy of spirit, the science of the idea as it returns to itself from its otherness (p. 54).
[D]ifferences among the various philosophical sciences are only determinations of the idea itself, and it is thus only the idea that manifests itself in these different elements. In nature it is not an other that needs to be recognized as the idea; the idea is in the form of alienation; in the spirit, the same idea has asserted itself as being for itself and becoming in and for itself (p. 55).
Hegel, Georg Wilhelm Friedrich. Encyclopedia of the Philosophical Sciences in Outline, and Critical Writings. Edited by Ernst Behler. Translated by Steven A Taubeneck. New York: Continuum, 1990.