Hamlet appears to be insane, after Polonius's death, in act IV scene II. There are indications, though, that persuade me to think other wise. Certainly, Hamlet has plenty of reasons to be insane at this point. His day has been hectic--he finally determined Claudius had killed his father, the chance to kill Claudius confronted him, he comes very close to convincing Gertrude that Claudius killed his father, he accidentally kills Polonius, and finally the ghost of his father visits him. These situations are enough to bring Hamlet to insanity, but he remains sharp and credible.…
