Holman Hunt portrays Christ standing at the door, the one who waits to find a welcome in the human heart. The picture takes its inspiration from words in the Book of Revelation, Behold I stand at the door and knock. The door, the threshold, is a powerful and evocative image. Neither on the inside nor the outside but in some ways both, the threshold is the boundary, the interface. And we live at such a boundary or interface between the present and the future, between what is and what is to come. Advent names such living where Christians live waiting the one who is to come. What is true of Advent living is true of life itself.
To live and to learn we need to have courage and patience to live at the edge, drawing on all that we have already received so we can be ready to discover the new. In Tennyson’s Ulysses, it’s not a door but an arch that marks this point of transition between what is already known and what is to come.

I am a part of all that I have met;
Yet all experience is an arch wherethrough
Gleams that untravelled world, whose margin fades
For ever and for ever when I move.
From Ulysses, Alfred, Lord Tennyson

Tennyson’s words remind us that we can only enter the new by appropriating what we already know. Experience is we’re told the arch. It’s in part inside and also out. The word experience includes both what we have already experienced. Experience is also what presents itself, the coming, the new.
Learning and growing, as a child, a young person, an adult, means that we need to hang around that arch, patiently, courageously, beseechingly. As priest and poet R.S. Thomas puts it, the meaning is in the waiting. And maybe we can’t teach another person to wait at that archway of discovery of we’re not ready ourselves to wait ourselves patiently, courageously, beseechingly, for what is to come.