When William Cowper was ill and in need of care, the family of the Reverend Morley Unwin took him in. They cared for him for years in his illness.
The son, William Unwin, grew and became a minister. Cowper was to him something of mentor and elder brother to whom he would write with his ministerial questions, to which Cowper would respond with long, thoughtful, and affectionate letters.
But it was to Mary, the wife of Morley and the mother of William that Cowper became the most attached. When Morley died, Cowper remained in the home with William and Mary until William moved away for his ministerial duties.
The relationship of Cowper and Mrs. Unwin (as he referred to her when he wasn't addressing her in person) is hard to pin down. He said repeatedly that he loved her as a mother, which fits considering how she had nursed him for years during his illness. They were very intimate, but not in a sexual way. Their relationship was purely chaste throughout their lives. He lived in her home, but was much more than a boarder, or a guest. Yet he was less than a husband. However they both grew to depend on eachother to an extent that surpasses most married couples.
It is very interesting that in their stringently scrupulous Reformed circle, no one seems to have questioned the propriety of their co-habitation. Not the young Reverend Unwin. Not John Newton, their pastor (the author of Amazing Grace). No one seemed to think it inappropriate, which they would have at the first sign that Cowper and Mrs. Unwin had any relationship other than one like cousins, or siblings.
And their relationship does seem to have been much like affectionate cousins, helping eachother through the latter half of life. And yet the passionate attachment, on both sides, surpasses the 'cousin' standard.
Cowper's poetry covered an exceedingly wide variety of themes and subjects, from glowworms (fireflies), to sofas, from hefty theolougomenon to lengthy arguments for educational reform, from anti-slavery pleas to odes mourning the death of a goldfinch.
Let us ignore for the moment his many translations from the Italian, Latin, Greek and French. Of his own poetry I only know of one poem that expresses intense romantic love, and that is addressed to Mrs. Unwin. Interestingly, that is also one of only a half handful of sonnets that he wrote (again we must ignore his translations). He wrote quite a few poems to Mary Unwin, on a variety of occasions, but they were never sonnets and they were never romantic. They were friendly and joking and playful, sometimes written to thank her for some gift or other. But they were not passionate.
Until this one. A sonnet. Passionate. Of love that would, in this life, always be not quite fulfilled.
SONNET TO MRS. UNWIN
Mary! I want a lyre with other strings;
Such aid from heaven as some have feign'd they drew;
An eloquence scarce given to mortals, new,
And undebased by praise of meaner things,
That, ere through age or woe I shed my wings
I may record thy worth, with honor due,
In verse as musical as thou art true,--
Verse that immortalizes whom it sings.
But thou hast little need; there is a book
On which the eyes of God not rarely look;
A chronicle of actions, just and bright;
There all thy deeds, my faithful Mary, shine,
And since thou own'st that praise, I spare thee mine.
Why for this one did he have to write a sonnet? When his other poems to her were not sonnets? When his other poems in general were not sonnets? He seems to have felt, what most other poets have felt, that sonnets are particularly (though not exclusively) suited to love-from-a-distance.
I am still wrestling with this idea, for though it seems clear that a vast majority of poets have assumed it, Milton, Donne, Herbert, and Hopkins all proved that it is not a strict limitation to the sonnet.