the mind of day

When I was looking for something else, a poem with the word "blindly" in it, I came across this poem by W.S.Merwin.

I have loved his poetry for a long time, and puzzled over many of his poems. This one really haunts me:

By Dark   by W.S. Merwin

When it is time I follow the black dog
into the darkness that is the mind of day

I can see nothing but the black dog
the dog I know going ahead of me

not looking back oh it is the black dog
I trust now in my turn after the years

when I had all the trust of the black dog
through an age of brightness and through shadow

on into the blindness of the black dog
where the rooms of the dark were already known

and had no fear in them for the black dog
leading me carefully up the blind stairs.