The Philosophy of Law: Public Right, § 48: Mutual Relations and Characteristics of the Three Powers
The three Powers in the State, as regards their relations to each other, are, therefore—(1) co-ordinate with one another as so many Moral Persons, and the one is thus the Complement of the other in the way of completing the Constitution of the State; (2) they are likewise subordinate to one another, so that the one cannot at the same time usurp the function of the other by whose side it moves, each having its own Principle, and maintaining its authority in a particular person, but under the condition of the Will of a Superior; and, further, (3) by the union of both these relations, they assign distributively to every subject in the State his own Rights.
Considered as to their respective Dignity, the three Powers may be thus described. The Will of the Sovereign Legislator, in respect of what constitutes the external Mine and Thine, is to be regarded as irreprehcnsible; the executive Function of the supreme Ruler is to be regarded as irresistible; and the judicial Sentence of the Supreme Judge is to be regarded as irreversible, being beyond appeal.