“To comprehend what is, is the task of philosophy: and what is is Reason.”
Works, VII, 17.
Context: The great thing however is, in the show of the temporal and the transient to recognize the substance which is immanent and the eternal which is present. For the work of Reason (which is synonymous with the Idea) when considered in its own actuality, is to simultaneously enter external existence and emerge with an infinite wealth of forms, phenomena and phases — a multiplicity that envelops its essential rational kernel with a motley outer rind with which our ordinary consciousness is earliest at home. It is this rind that the Concept must penetrate before Reason can find its own inward pulse and feel it still beating even in the outward phases. But this infinite variety of circumstances which is formed in this element of externality by the light of the rational essence shining in it — all this infinite material, with its regulatory laws — is not the object of philosophy.... To comprehend what is, is the task of philosophy: and what is is Reason.
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Georg Wilhelm Friedrich Hegel 106
German philosopher 1770–1831Related quotes

72
Golden Sayings of Epictetus
Variant: It is impossible for a man to learn what he thinks he already knows.

“The sole remaining task for philosophy is the analysis of language.”
Though this has been quoted extensively as if it were a statement of Wittgenstein, it was apparently first published in A Brief History of Time (1988) by Stephen Hawking, p. 175, where it is presented in quotation marks and thus easily interpreted to be a quotation, but could conceivably be Hawking paraphrasing or giving his own particular summation of Wittgenstein's ideas, as there seem to be no published sources of such a statement prior to this one. The full remark by Hawking reads:
: Philosophers reduced the scope of their inquiries so much that Wittgenstein, the most famous philosopher of this century, said, “The sole remaining task for philosophy is the analysis of language.” What a comedown from the great tradition of philosophy from Aristotle to Kant!
Disputed

“The task of philosophy is to recover the totality obscured by the selection.”
Pt. I, ch. 1, sec. 6.
1920s, Process and Reality: An Essay in Cosmology (1929)
Context: Philosophy is the self-correction by consciousness of its own initial excess of subjectivity. Each actual occasion contributes to the circumstances of its origin additional formative elements deepening its own peculiar individuality. Consciousness is only the last and greatest of such elements by which the selective character of the individual obscures the external totality from which it originates and which it embodies. An actual individual, of such higher grade, has truck with the totality of things by reason of its sheer actuality; but it has attained its individual depth of being by a selective emphasis limited to its own purposes. The task of philosophy is to recover the totality obscured by the selection.

“Undoubtedly, philosophy caused the Revolution. But what caused philosophy? Theological arrogance.”

Dijkstra (2000), "Answers to questions from students of Software Engineering" http://www.cs.utexas.edu/~EWD/ewd13xx/EWD1305.PDF (EWD 1305).
2000s

“But what a perfection of rottenness in a philosophy!”
William James, of Santayana's The Interpretations of Poetry and Religion (1900), in a letter to George H. Palmer (1900), as quoted in George Santayana : A Biography (2003) by John McCormick
Misattributed

“Science is what we know, and philosophy is what we don't know.”
1950s, Unpopular Essays (1950)