Hollow

The other week, the following lines were quoted in Doctor Who (the episode entitled "The Lazarus Experiment"):

Between the idea
And the reality
Between the motion
And the act
Falls the Shadow

It's from The Hollow Men, by TS Eliot. I've studied Eliot more than any other poet, but not this poem in particular.

I'll be reading it more carefully in days to come. It seems, these days, I'm encountering the Shadow every way I turn.