Does the last line of the first stanza of Katherine Philips's poem, To Mrs. M. A. at parting have a grammatical error?
It's surprising that a renowned poet and translator at that time would use the wrong pronoun to fit the rhyme. Or am I mistaken here?
I HAVE examin'd and do find,
Of all that favour me,
There's none I grieve to leave behind
But only, only thee.
To part with thee I needs must die,
Could parting sep'rate thee and I.
Would the poet's contemporaries have seen the construction as ungrammatical or non-standard (though acceptable in a poem) or was it more generally acceptable then than it is now?
If you think the subjective first-person singular pronoun "I" was only used in the last line due to "poetic license," please post that as an answer and provide evidence that the structure was considered ungrammatical outside of poetic contexts at the time the poem was written.