In brief: Something other than what happens in studying a law of nature. Whoever thinks gravitation thinks an alien necessity to which he is subject as a body. Whoever follows the Groundlines through thinks the structure of his own freedom — and in doing so acquires a standard against which what exists can be measured.
The object is not alien
The thinking of the understanding has to do with laws for objects: planets, stones, cells. These laws are not the essence of the one who thinks them; he is subject to them. The object of the philosophy of right is another. What is followed through here is why freedom needs property (§ 41 ff.), why property leads to contract (§ 72 ff.), why conscience alone will not bear the weight (§ 137–§ 140), and why the institutions of ethical life are needed in order to be actually free (§ 142 ff.).
This is not passive reception but what Hegel calls the „exertion of the concept“. And because the object is one’s own freedom, the carrying out changes something in the one who carries it out.
1. The act: distinguishing essence from contingency
Following the argument through is a critical act, and it hangs on a sentence more often misunderstood than read: „What is rational is actual; and what is actual is rational“ (Preface).
It does not say that everything existing is rational. Mere existence — the actually existing state — is full of contingency, defects and historical limitation. „Actuality“ means in Hegel the reason that is at work in this defective existence and that has to prevail in it. At length: „What is rational is actual“ — does Hegel thereby justify everything that exists?
Whoever has the distinction has a standard. The weaknesses of the actual state can then be named for what they are: a failure of existence to meet its own concept. That is a sharper criticism than the cynic’s, who rejects everything — for it can state what the measure is.
2. The result: holding out the tension
The goal is reconciliation, and that is not assent to what exists. It consists in understanding oneself neither as alienated — the world is not senseless, there is reason at work in it — nor as an apologist: not everything is well as it is.
What remains is the consciousness that holds both together: the necessity of reason and the contingency of existence. Hegel calls that freedom; one may also describe it as a demand hard to meet, for the tension is not dissolved but held out.
3. The practical consequence
Two forms of unfree action fall away. Abstract rebellion, which rejects what exists as a whole — § 5 Remark shows that it can only destroy, and destroys with it the ethical ground on which it itself stands. And cynical resignation, which withdraws because everything is supposedly senseless — it has no standard and therefore cannot formulate an objection either.
What remains is unspectacular: to act within the institutions — in one’s occupation, in public life, in the corporations — in order to bring existence closer to its concept. Hegel himself calls this cultivation, and means by it not learning but the capacity to relate one’s own particularity to something universal.
And it helps against a particular error: taking the temporary victory of particular interests for the truth. Whoever has once drawn the distinction between existence and actuality does not make it again.
Sources. Groundlines, Preface; § 5 Remark, § 41 ff., § 72 ff., § 137–§ 140, § 142 ff., § 187 (cultivation), § 250–§ 256. – Encyclopaedia (1830) § 6 Remark (distinction of actuality and appearance), § 24 Addition. – Phenomenology of Spirit, Preface („exertion of the concept“). – In the glossary: Actuality and Rationality, Reconciliation, Culture and Cultivation.