QuestionsCan we be certain of anything?What is rational is actual
Can we be certain of anything?Yes, through reason

What is rational is actual

Georg Wilhelm Friedrich Hegel 1770 · 1831The real is rational: Spirit realises itself in history.
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What it claims

Reason can know reality: the task of philosophy is to understand what is ("its time apprehended in thought"), not to teach the world what it ought to be.

Why

"Real" in the strong sense is not everything that exists: chance and error exist without being real, and what is real is rational.

In short

"What is rational is actual" is an argument by Georg Wilhelm Friedrich Hegel (Philosophy of Right, Preface (1820); Encyclopaedia, § 6 Remark) on the question "Can we be certain of anything?" (answer: yes, through reason). Its claim: Reason can know reality: the task of philosophy is to understand what is ("its time apprehended in thought"), not to teach the world what it ought to be. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P4). AskPhilosophy presents 4 objections, 1 of them with a documented reply, and the original text behind each premise, checked word for word.

Philosophy of Right, Preface (1820); Encyclopaedia, § 6 Remark
Valid with an implicit premise

Hegel's most debated sentence. For him, reason is not a powerless ideal locked in our heads: it is at work in the world. Philosophy can therefore know reality, and its task is to understand what is, not to say how the world ought to be. Mind the word "actual": Hegel writes wirklich (effective, what truly acts), which he distinguishes from whatever merely exists. From 1821 he was accused of justifying the Prussian state; he replied in 1827, in the Encyclopaedia.

P1What is rational is actual, and what is actual is rational: the Idea is not so powerless that it merely ought to be without existing.
P2"Actual" does not mean everything that exists: existence is only partly actuality. Chance, error and evil exist without being actual in the strong sense.
P3Philosophy is reason thinking itself: its object is the Idea, the rational.
P4 · implicit premiseIf the rational is actual, thinking reason finds its object in the present world, not in a beyond of its own invention.
Therefore reason can know reality: the task of philosophy is to understand what is ("its time apprehended in thought"), not to teach the world what it ought to be.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P4, the computer finds a world where the rational is actual and philosophy thinks the rational, but looks for its object outside the present, for instance in a future ideal: its task could then be to prescribe.
Valid with P4, the bridge Hegel assumes between "the rational is actual" and "philosophy must understand the present". P2 is not needed for the conclusion's logic, but it blocks the misreading: if "actual" meant "everything that exists", P1 would justify any injustice. The whole debate is about P1 and the blurry line between what is "actual" and what merely exists.
Analogy. A doctor does not invent an ideal body to compare with yours: he looks at how your body really works, what in it is alive, and he distinguishes the disease (which exists, but is not "the" body). For Hegel, the philosopher does the same with a society: he looks for the reason that makes it live, not a dreamed-up plan.

Objections

4

Each objection is a conversation: click to see who replies and where the debate stands.

C
Critics in his lifetime: the conservative reading 1821 · attacks premise 1

If everything actual is rational, then the established order, the Prussian state and its injustices are justified. The formula forbids criticism and serves power. (Hegel himself notes that these sentences "struck" people and met with hostility; Rudolf Haym repeated the charge in 1857.)

Hegel replies
Hegel
Hegel replies in 1827: he has elsewhere distinguished actuality from what merely exists. A contingent existence is worth no more than a mere possibility, which might just as well not be. And who does not see around him many things that are not as they ought to be?
The debate goes on (our summary) His critics note that Hegel does not say what criterion distinguishes the "actual" from the merely "existing" in an institution: the line remains in the philosopher's hands. And the same text adds that criticising such defects is not philosophy's business.
Schopenhauer, On the Freedom of the Will (written 1838-39, quoted from the revised edition of 1860) 1860 · attacks the conclusion

Hegel turned philosophy, "the daughter of reason", into a tool serving the ends of the state and of obscurantism, hidden under the "emptiest verbiage". Applied to our argument (Schopenhauer does not comment on this sentence here): a philosophy content to "understand what is" has given up the free search for truth.

no reply
No reply possible: objection raised in 1860, after the author's death (1831).
The debate goes on (our summary) The tone is very personal: in 1820, in Berlin, Schopenhauer had scheduled his lectures at the same hour as Hegel's, and almost no one came. We quote the 1860 text: we do not have the 1841 edition to check whether the sentence was already there. Historians also point out that the state Hegel describes (constitution, juries, public opinion, subjective freedom) was not the actual Prussia of 1820.
Marx, Theses on Feuerbach 1845 · attacks the conclusion

Understanding the world is not enough. If philosophy always arrives "too late", like the owl of Minerva, it condemns itself to blessing what is. Philosophers have only interpreted the world; the point is to change it.

no reply
No reply possible: objection raised in 1845, after the author's death (1831).
The debate goes on (our summary) Hegel's defenders reply that understanding is not approving, and that Marx himself owes Hegel the idea that reality contains contradictions pushing it beyond itself.
J
Johannes Climacus (Kierkegaard's pseudonym), Postscript 1846 · attacks premise 1

A logical system is possible, but not a system of existence. Reality can be grasped whole only by God; for an existing being it stays open and unfinished. By wanting all reality to be rational, the system forgets the individual who has to live and choose.

no reply
No reply possible: objection raised in 1846, after the author's death (1831).
The debate goes on (our summary) For Hegel's readers, he never claimed that every detail of existence is rational (P2 says so); but Kierkegaard replies that it is precisely this "detail", the individual, that matters.