I did think Shakespeare at first but thought it was a catch so I took a guess at Robbie Burns. Then Jock gave the second line that convinced me that it was Shakespeare and the timbre of the poem put me in mind of 'Romeo and Juliet'. I have never studied Shakespeare, even in school, just picked it up as I went along.
Now who said this:- "I disagree with all that you have said, I think you are completely wrong. But I will defend until death your right to say it." A clue, it was not originally in English.