Below is an excerpt from, "The Soul of Kierkegaard: Selections from His Journals." Edited by Alexander Dru. Dover Publications, Inc: Mineola, New York. 2003. Pg. 142-43.
Here again is one of the most important points regarding man's relation to God.If it were possible to have a physical certainty that God would use one as an instrument (like a king his minister)---how could it be possible not to submit willingly to every sacrifice. But is it possible to have a real certainty, or even a purely immediate certainty of one's relation to God. For God is spirit. One can only have a spiritual relationship to a spirit; and a spiritual relationship is eo ipso dialectical.---How an Apostle understands himself in having been called by a revelation and in having an immediate certainty which cannot in any way be dialectical, I do not understand---but it can be believed. I understand an ordinary man's relation to God and to Christ, Socratically. Socrates did not know with certainty whether he was immortal. (Oh, the rogue, for he knew that immortality was a spiritual qualification and eo ipso dialectical, and beyond all immediate certainty. So that even though he did not know to what degree he was immortal---which so many dunces know exactly---he knew what he was saying.) But his life expresses the fact that there is an immortality and that he himself was immortal. The question of immortality, he says, concerns me so infinitely, that I stake everything on that "if."