The Rainbow by William Wordsworth:
My heart leaps up when I behold
A Rainbow in the sky:
So was it when my life began;
So is it now I am a man;
So be it when I shall grow old,
Or let me die!
The Child is father of the man;
And I wish my days to be
Bound each to each by natural piety.
I am trying to understand, why there is no "the" before "father" in this poem? Would you please explain the reason?