1 Verily, verily, I say unto you, He that entereth not by the door into the sheepfold, but climbeth up some other way, the same is a thief and a robber.Not previously having given this much thought, I'd assumed that the point of the opening verses here is to say: only by entering licitly and in good gaith into the proper ways of the Christian church can you be saved (like the wicked man in Bunyan's Pilgrim's Progress who leaps over the wall at the beginning rather than going through the straight gate, undergoes all the trials of the progress himself and gets to the city of Zion, only to be carried off to hell at the last minute). But the emphasis, here, is not on the ordinary Christian: it is on Christ himself, or at a pinch, on his pastors: bishops and priests and whatnot. The regular Christian need not worry about this gate; the parable only concerns those who would seek to lead regular Christians (although, according to the logic of the tale, the wicked man would have no luck breaking into the sheep fold; the sheep would never follow 'a stranger' -- which makes the trope of the fence and gate and so on rather redundant). But the confusion is in verse 9, when Christ, having symbolised himself as a shepherd coming through the gate, goes on to symbolise himself as the gate as well. Christ enters the world as the good shepherd, but does so through Christ: a kind of sacramental existential short-circuit.
2 But he that entereth in by the door is the shepherd of the sheep.
3 To him the porter openeth; and the sheep hear his voice: and he calleth his own sheep by name, and leadeth them out.
4 And when he putteth forth his own sheep, he goeth before them, and the sheep follow him: for they know his voice.
5 And a stranger will they not follow, but will flee from him: for they know not the voice of strangers.
6 This parable spake Jesus unto them: but they understood not what things they were which he spake unto them.
7 Then said Jesus unto them again, Verily, verily, I say unto you, I am the door of the sheep.
8 All that ever came before me are thieves and robbers: but the sheep did not hear them.
9 I am the door: by me if any man enter in, he shall be saved, and shall go in and out, and find pasture.
10 The thief cometh not, but for to steal, and to kill, and to destroy: I am come that they might have life, and that they might have it more abundantly.
11 I am the good shepherd: the good shepherd giveth his life for the sheep.
I think we've been getting this the wrong way about. The door is not 'from' the wider world 'into' the safety of the sheep-fold; for our world, though large, is finite and God infinite. The door is 'from' the smaller place to the larger (larger, indeed, is something of a misnomer): it leads out, not in.