Read the passage from Act V of Hamlet.

Hamlet: Let me see.—[Takes the skull.]—Alas! poor Yorick. I knew him, Horatio; a fellow of infinite jest, of most excellent fancy; he hath borne me on his back a thousand times; and now, how abhorred in my imagination it is! my gorge rises at it. Here hung those lips that I have kissed I know not how oft.

The main topic of the passage is