Anti-Climacus argues that the Christian category of sin raises the measure of despair to its maximum. In purely philosophical terms, despair is the failure of the self to be what it is; in Christian terms, sin is the failure of the self before God — the refusal, in full awareness of God's offer of reconciliation, to accept that offer. The Christian doctrine of sin is therefore more demanding than any philosophical account of self-failure: it requires not only self-awareness but awareness of God, and it names as sin not only ignorance or weakness but the clear-eyed refusal of grace.
The absolute paradox — God appearing as a particular human being, the eternal entering time — is designed to offend reason. There is no way to approach it neutrally: one either leaps into faith or recoils into offence. Offence is not the absence of a relation to Christ but a particular kind of relation — a repelled attention, a scandalised refusal that cannot simply look away. Anti-Climacus identifies two forms of offence: passive offence, which does not want the paradox to be true; and active offence, which goes on the attack against the claim. Neither is indifference; both are existentially engaged with what they reject.
Anti-Climacus positions The Sickness Unto Death at a higher level of Christian consciousness than Kierkegaard claimed to have reached himself. The work diagnoses despair and points toward faith with the clarity of one who sees from above; Kierkegaard, in his own person, claimed to be a poet of the religious — one who described faith from outside it and pointed toward it without securely possessing it. This deliberate positioning of the pseudonym above the author is itself an act of indirect communication: the reader is invited to see that genuine faith surpasses both the author and the analysis.
The concept of offence in relation to faith is developed throughout Part Two of The Sickness Unto Death, which is also the most explicitly theological section of the authorship. The related analysis of the absolute paradox appears in Philosophical Fragments (1844), also written under the pseudonym Johannes Climacus.