Get thee to a nunnery
Hamlet:
I did love you once. Ophelia:
Indeed, my lord, you made me believe so. Hamlet:
You should not have believ'd me, for virtue cannot so
inoculate our old stock but we shall relish of it. I lov'd you not. Ophelia:
I was the more deceiv'd. Hamlet:
Get thee to a nunn'ry, why woulds't thou be a breeder of
sinners?
In this heartbreaking scene, it's hard to tell how much of what Hamlet says is sincere, and how much an act [see ANTIC DISPOSITION]. The critics have never ceased arguing this question. We do know that his mother's recent remarriage has intensified Hamlet's sexual revulsion—he's recently likened the sexual act to tumbling in a sty.
Here, the prince denies ever having loved Ophelia, right after claiming that he did love her once. This may be just a game Hamlet is playing, but perhaps he means that what seemed like love to him once now seems false and repulsive. Using a horticultural metaphor, he casts doubt on his own motives: the "old stock" (original nature) of man is so corrupt that the grafting of virtue can never wholly eradicate the "relish" (taste) of corruption. In his famous line "Get thee to a nunn'ry," he exhorts Ophelia to put herself away so that she may never breed sinners like Hamlet.
Specialists in Shakespeare's bawdy language are fond of noting that "nunnery" was common Elizabethan slang for "brothel," and that therefore Hamlet's command is ironic and even more despairing than it seems. The pun would accord with the paradoxical nature of the prince's speech, but there is little evidence elsewhere in the scene that Hamlet intends a double entendre.