In Hamlet , what does he mean when he tells Rosencrantz & Guildenstern?

Question

"I am mad north/northwest,when the wind is southerly, I know a hawk from a handsaw'.

"......I know a hawk from a handsaw." Is this some sort of riddle or old english phrase?

Answer 1

The following quotation from Bernard Lott's 1968 New Swan edition suggests that it was an old English saying, but one that has not survived.

"Hamlet clearly means that on other occasions (when the wind is blowing from another quarter) his powers of discernment are as good as anyone else's. Two explanations of the hawk and handsaw are suggested
(i) handsaw should be hernshaw, another name for heron...Then the hawk, a bird of prey, is imagined as chasing the heron; the heron, as birds of heavy flight geenrally do, flies with the wind to escape pursuit; and if the wind is blowing from the south, the bird will be flying away from the sun. The hunter will be able to distinguish them, therefore, since he will have his back to the sun and not be dazzled by it.
(ii) hawk, as a variant of hack, is used (but not elsewhere in Shakespeare) to refer to the square board with a handle used by plasterers to hold their plaster as they are working with it. The phrase could then simply refer to Hamlet's ability to distinguish one tool (one thing) from another.

Neither explanation has any particular link with the patterns of imagery in the play, and the phrase may, perhaps, demand another explanation which we know nothing of. It has a proverbial sound, with the alliteration of the h's; and, in favour of the explanation to do with birds, it should be added that a proverb to do with distinguishing birds is known from a book of about the same date as Hamlet: ' [She] doth not knowe a Buzzard from a Hawke.' "

My personal gut feeling is that it's supposed to be deliberately obscure - the elliptical language Hamlet uses underlines his distrust of R and G in particular, and everyone in the corrupt Danish court generally - he's scared to speak in plain language, for fear of being betrayed.

Answer 2

that he is only mad part of the time.