Dry the pool, dry concrete, brown edged,
And the pool was filled with water out of sunlight,
And the lotos rose, quietly, quietly,
The surface glittered out of heart of light,
And they were behind us, reflected in the pool.
This is beautiful. I don't think it can harm these lines to say that the lotos is like an avatar of the rose (the lotos rose), and its appearance as a miracle is a glimpse of a way of being human, of living in a human mind, which Eliot longs for. I think this way of being is to live entirely in the ecstasy of the moment, without clinging. It is like a flash of joy. The dry empty heart fills up with bright water. Now I am thinking of Auden: 'In the desert of the heart, let the healing fountains start'.
And 'they' (the ghosts of the past, the lost children) are 'behind us'. We only see them as reflections in the light of the present moment. They are not discarded, nor do they possess us, they are in their right place, in the past. We are reconciled momentarily with everything.
Then a cloud passed, and the pool was empty.
Go, said the bird, for the leaves were full of children,
Hidden excitedly, containing laughter.
Go, go, go, said the bird: human kind
Cannot bear very much reality.
But Eliot can not live in that way. Theologically, he doubts that human beings can achieve enlightenment on their own efforts (which is why he rejected Buddhism). Psychologically he finds he can only live in that joy for a few tantalising seconds and then it is swept away. The child-ghosts are excited rather than calmed, the leaves are full of laughter.
The bird appears again. It is a messenger of the gods, and it is a frisky taunting intellectual messenger like Hermes. This time like an angel it drives him out of the garden.
Time past and time future
What might have been and what has been
Point to one end, which is always present.
And so, in the last lines of the stanza, he has returned to where he began the poem. He is caught in a destructive trap, by virtue of being human, and he can not escape the trap by his own efforts. Every second is being burnt up, and he can't experience that as ecstasy, only as a continual death and loss.