The satirical rogue says here that old men have grey beards, that their faces are wrinkled[…]and that they have a plentiful lack of wit together with most weak hams (II.ii.193-7)
When Polonius asks Hamlet what he is reading, Hamlet teases Polonius by pretending that his book is about old men. Hamlet frequently dwells on the physical and mental deterioration that comes with age. In other ways, too, this scene reveals Hamlet’s obsession with decay. He compares human conception and childbearing to “maggots in a dead dog” (II.ii.).
O, my offence is rank; it smells to heaven
In a soliloquy—the only soliloquy in the play not spoken by Hamlet—Claudius admits murdering his brother, and he describes his guilt in the language of decay. His crime smells bad, like something going off. Throughout Hamlet, moral faults are described in the language of rot, decay and disease. The Ghost’s “foul crimes” must be “purged away” (I.v: purging was a Renaissance medical procedure) and Gertrude sees “black and grievèd spots” (III.iv.) on her soul. This line creates a sense that the decay and sickness which infects everything in Hamlet has a spiritual dimension: the characters are not just doomed to die but doomed to damnation.
Alas, poor Yorick. I knew him, Horatio
This line—one of the most famous in literature—is prompted by Hamlet’s discovery that the skull he is holding belongs to his father’s former fool, Yorick. In a play obsessed with death and decay, the appearance of an actual skull on stage is a climactic moment, and it causes Hamlet to meditate at length on the horror of decomposition: “My gorge rises at it” (V.i.). Hamlet remembers Yorick’s “gambols, your songs, your flashes of merriment” (V.i.), which creates an eerie effect: none of Hamlet’s other characters could be described as jolly, but Yorick’s skull is still “grinning” (V.i.).