We are like eggs

When he said 'Be perfect ,' He meant it.
He meant that we must go in for the full treatment...

It may be hard for an egg to turn into a bird:
it would be a jolly sight harder
for it to learn to fly while remaining an egg.

We are like eggs at present.
And you cannot go on indefinitely
being just an ordinary, decent egg.
We must be hatched or go bad."

Mere Christianity p.155