Tonight as I prepared to preach on St. John 14, and I stumbled upon something I hadn't noticed before: Jesus' reference to his father's house is in all probability not a mere reference to heaven, though I had glossed over it a thousand times with that thought firmly embedded in my mind. But it dawned on me: Jesus never refers to heaven as "my father's house." Rather, the only other reference I can think of is in the Gospel of his lingering behind in Jerusalem at the age of twelve. His response to his mother is, "Did you not know that I must be in my Father's house." There, it certainly is not a reference to heaven, but to the temple. That is Jesus' Father's house.
What, then, are the many mansions? Many rooms -- what are these? The context is the upper room, and the extended discourse deals with immediate future, Jesus' going to his Father, and the coming of the Holy Spirit. All this has to do, ultimately, with the inauguration of the Apostolic Ministry.
Thus, in short, a shift occurs at the completion of Jesus' ministry, culminating in his death and resurrection. The shift may be explained this way: no longer is there one temple. No longer is Jesus preaching and ministering in one place at a time. Now his Father's house has many rooms. Wherever Jesus is preached by his Apostolic Ministers, there is a mansion, and there is the way, the truth, and the life.