In my first two posts on Harnack, I have focused on his hermeneutical method and his fundamental presupposition. His hermeneutical method is to interpret the Christian religion by distinguishing the kernel of what is essential from the husk of Christianity's various historical and cultural forms.
Harnack's fundamental presupposition is that religious experience is primary, whereas doctrine is a secondary process that inevitably obscures the heart-felt reality of the experience. Harnack laments, "How often does it happen in history that theology is only the instrument by which religion is discarded!" (p. 48).
This brings us then to the heart of the matter. If it is not doctrine, what does Harnack think the essence of Christianity to consist in? To answer this question, he appeals to the message of Jesus himself. He argues that the message of Jesus can be summarized under three main heads (p. 51):
(1) The kingdom of God and its coming
(2) God the Father and the infinite value of the human soul
(3) The higher righteousness and the commandment of love
Let's begin with the first point: The kingdom of God and its coming.
Harnack sees two strands in Jesus' teaching concerning the kingdom of God. The first strand is the nationalistic, apocalyptic teaching concerning a future drama in which the kingdom of this world is destroyed and God's kingdom is set up in glory. This future kingdom only comes through a cosmic battle between God and Satan. To this strand belong the parts of Jesus' teaching in which he pictures himself as seated at God's right hand, with his twelve disciples on thrones judging the twelve tribes of Israel. This apocalyptic conception of the kingdom is one that Jesus himself did not originate; he simply inherited it from his Jewish context and shared it with his contemporaries.
The second strand is very different. In this strand, the kingdom of God is present, not future. It is most clearly expressed in Luke 17:20-21: "Being asked by the Pharisees when the kingdom of God would come, he answered, 'The kingdom of God is not coming with signs to be observed, nor will they say, "Look, here it is!" or "There!" for behold, the kingdom of God is in the midst of you'" (ESV). Harnack writes that the kingdom, on this view, is "a still and mighty power in the hearts of men" (p. 54).
How are we to reconcile the two strands? I'm sure you can guess the answer. The first strand is the husk, whereas the second strand is the kernel. The first strand is simply traditional Jewish eschatological thinking; the second is peculiar to Jesus and represents his true message. Harnack sweeps away the husk as irrelevant and proposes that we focus only on Jesus' teaching concerning the kingdom as a spiritual power in the hearts of men.
He appeals to the parables of Jesus to flesh this out:
If anyone wants to know what the kingdom of God and the coming of it meant in Jesus' message, he must read and study his parables. He will then see what it is that is meant. The kingdom of God comes by coming to the individual, by entering into his soul and laying hold of it. True, the kingdom of God is the rule of God; but it is the rule of the holy God in the hearts of individuals; it is God himself in his power. From this point of view everything that is dramatic in the external and historical sense has vanished; and gone, too, are all the external hopes for the future. Take whatever parable you will, the parable of the sower, of the pearl of great price, of the treasure buried in the field--the word of God, God himself, is the kingdom. It is not a question of angels and devils, thrones and principalities, but of God and the soul, the soul and its God (p. 56).