Here’s a wonderful little snippet from a sermon preached by Karl Barth in November 1934 in which he compares Jesus and ghosts.
‘And when the disciples saw him walking on the sea, they were troubled, saying, “It is a ghost!” And they cried out for fear!’ (Matt 14:26)
What has happened then? Jesus came to them. And they, his people, don’t recognise him. They don’t realise that it is he who is coming towards them, but think they are seeing a ghost—which in this context means a figment of their imagination—and they are afraid and cry out. To be sure, if it were really a figment of their imagination, a ghost, which they had encountered here, they would certainly have had cause to be afraid. A Jesus who is not really Jesus but a figment of the pious imagination, the product of our revolutionary or reactionary dreams, the mirage of our hopelessness or our enthusiasm—a Jesus like this certainly may and must be feared, for in fact this imaginary Jesus could only magnify the distress we experience in our lives and in the church. If this is an imaginary Jesus, or a ghost, there is certainly reason to be afraid, for then the turmoil human beings are in can, without fail, only increase. And the more passionately this Jesus is believed and proclaimed, the deeper will be the distress, the darker the night in which the church finds itself. Better no Jesus at all than a ghost like that, a figment of the imagination.
Karl Barth, The Word in this World: Two Sermons by Karl Barth, 57.