Kierkegaard criticizes the Hegelian notion that faith and knowledge are synonymous, that faith is the immediate. Faith, Kierkegaard asserts, is the mediate. It is the bridge that spans the chasm between offense and inwardness. If it were a case of a lack of knowledge, knowledge, that is, Hegelian faith, would be a direct response. But since deity is beyond our reckoning, as is the incarnation of the God-man, knowledge is insufficient.
Faith is a volitive act that transcends knowledge.
It is inwardness. Precisely Because the God-Man is the Possibility of Offense. An idol is something static. It can be seen and believed directly. The ineffable incarnated God cannot be known directly.