It is impossible to exaggerate the importance that this problem had for Hegel. It is true that his early theological writings contain hard sayings about Christianity and the churches; but the object of his attack was orthodoxy, not theology itself. All that he wrote at this period throbs with a religious conviction of a kind that is totally absent from Kant and Hegel’s other 18th-century teachers. Above all, he was inspired by a doctrine of the Holy Spirit. The spirit of humanity, its reason, is the candle of the Lord, he held, and therefore cannot be subject to the limitations that Kant had imposed upon it. This faith in reason, with its religious basis, henceforth animated the whole of Hegel’s work.

His outlook had also become that of a historian—which again distinguishes him from Kant, who was much more influenced by the concepts of physical science. Every one of Hegel’s major works was a history; and, indeed, it was among historians and classical scholars rather than among philosophers that his work mainly fructified in the 19th century.

When in 1798 Hegel turned back to look over the essays that he had written in Berne two or three years earlier, he saw with a historian’s eye that, under Kant’s influence, he had misrepresented the life and teachings of Jesus and the history of the Christian church. His newly won insight then found expression in his essay “Der Geist des Christentums und sein Schicksal” (“The Spirit of Christianity and Its Fate”), likewise unpublished until 1907. This is one of Hegel’s most remarkable works. Its style is often difficult and the connection of thought not always plain, but it is written with passion, insight, and conviction.

He begins by sketching the essence of Judaism, which he paints in the darkest colours. The Jews were slaves to the Mosaic Law, leading a life unlovely in comparison with that of the ancient Greeks and content with the material satisfaction of a land flowing with milk and honey. Jesus taught something entirely different. Humans are not to be the slaves of objective commands: the law is made for them. They are even to rise above the tension in moral experience between inclination and reason’s law of duty, for the law is to be “fulfilled” in the love of God, wherein all tension ceases and the believer does God’s will wholeheartedly and single-mindedly. A community of such believers is the Kingdom of God.

This is the kingdom that Jesus came to teach. It is founded on a belief in the unity of the divine and the human. The life that flows in them both is one; and it is only because humans are spirit that they can grasp and comprehend the Spirit of God. Hegel works out this conception in an exegesis of passages in the Gospel According to John. The kingdom, however, can never be realized in this world: humans are not spirit alone but flesh also. “Church and state, worship and life, piety and virtue, spiritual and worldly action can never dissolve into one.”

In this essay the leading ideas of Hegel’s system of philosophy are rooted. Kant had argued that humans can have knowledge only of a finite world of appearances and that, whenever their reason attempts to go beyond this sphere and grapple with the infinite or with ultimate reality, it becomes entangled in insoluble contradictions. Hegel, however, found in love, conceived as a union of opposites, a prefigurement of spirit as the unity in which contradictions, such as infinite and finite, are embraced and synthesized. His choice of the word Geist to express this his leading conception was deliberate: the word means “spirit” as well as “mind” and thus has religious overtones. Contradictions in thinking at the scientific level of Kant’s “understanding” are indeed inevitable, but thinking as an activity of spirit or “reason” can rise above them to a synthesis in which the contradictions are resolved. All of this, expressed in religious phraseology, is contained in the manuscripts written toward the end of Hegel’s stay in Frankfurt. “In religion,” he wrote, “finite life rises to infinite life.” Kant’s philosophy had to stop short of religion. But there is room for another philosophy, based on the concept of spirit, that will distill into conceptual form the insights of religion. This was the philosophy that Hegel now felt himself ready to expound.