“What is reasonable is real; that which is real is reasonable.”

Was vernünftig ist, das ist Wirklich; und was wirklich ist, das ist vernünftig.
Variant translation: What is rational is real; And what is real is rational. Upon this conviction stand not philosophy only but even every unsophisticated consciousness. From it also proceeds the view now under contemplation that the spiritual universe is the natural. When reflection, feeling, or whatever other form the subjective consciousness may assume, regards the present as vanity, and thinks itself to be beyond it and wiser, it finds itself in emptiness, and, as it has actuality only in the present, it is vanity throughout. Against the doctrine that the idea is a mere idea, figment or opinion, philosophy preserves the more profound view that nothing is real except the idea. Hence arises the effort to recognize in the temporal and transient the substance, which is immanent, and the eternal, which is present. The rational is synonymous with the idea, because in realizing itself it passes into external existence. It thus appears in an endless wealth of forms, figures and phenomena. It wraps its kernel' round with a robe of many colors, in which consciousness finds itself at home. Through this varied husk the conception first of all penetrates, in order to touch the pulse, and then feel it throbbing in its external manifestations. To bring to order the endlessly varied relations, which constitute the outer appearance of the rational essence is not the task of philosophy.
Georg Wilhelm Friedrich Hegel, Philosophy of Right as translated by SW Dyde, Queen’s University Canada, 1896, Preface xxvii-xxviii
Elements of the Philosophy of Right (1820/1821)