This famous line from Shakespeare's As You Like It (III, v, 82) is actually in quotation marks in the play. The line is a quote, of course, from Christopher Marlowe's Hero and Leander. The line is spoken by Phebe, a minor character in the play, a shepherdess who has fallen for Rosalind disguised as a young man, and whom another minor character, the shepherd Silvius, loves. What is interesting about the line is the one that precedes it, which is "Dead shepherd, now I find thy saw of might." And then comes the famous question. What I find fascinating about the two lines together is that Phebe should know of Marlowe's poem (who has died by the time of the story of the play) - nay, that she should have read it and be able to quote from it. This is highly unlikely, though nothing - it seems - is impossible in the Forest of Arden.
It is, obviously, Shakespeare himself who knows of and has read Marlowe's poem (who has died in 1593). This is a rare bit of scholarship on Shakespeare's part. And what is of further interest in the line is that in many of Shakespeare's plays love is frequently love at first sight. It seems that the Great Bard believed in this from Romeo and Juliet on through The Tempest. In that final Serene Romance, as it is usually called, love at first sight happens simultaneously to both Ferdinand and Miranda, just as it has also happened "long ago" to both Romeo and Juliet in that lovely "pathetic tragedy" where love cannot conquer all. And, indeed, in the annals of love, love at first sight is a wonderful thing. Would it always work in real life as well! There may well be times when it does, but what makes it sustain itself is another matter, a deep and abiding mystery. Scientists may question what poets seem to know for sure. And in our heart of hearts we are all, I think, poets when it comes to love, especially perhaps when it comes to love at first site.