The play begins with Marcellus referring to the ghost of Hamlet as a “thing” and Bernardo says it is “nothing” – this of course is the ghost of the former King Hamlet. Young Hamlet tells Horatio that the ghost is a “guilty thing”. Hamlet tells Polonius that he “cannot take anything that [he] would more willingly part withal, except [his] life”.
Apparently, things are everywhere in Hamlet, and something is definitely rotten in the state of Denmark. This “thing” is the king. In fact, if one were to chant the legalese of nobility that sets the king apart from the rest of the court, then the rhyme would be that “the king is a thing”. Remember that this is poetry, and Shakespeare plays with the words and sound of “thing” and “king”.
And yet, “thing” is the most ambiguous of terms lacking any sense of meaning, because a “thing” could be anything, nothing, and something. Check out the definition of “thing” and you will find more than 20 terms from object, to circumstance, to statement, to feeling, and…well…pretty well anything can be a thing. At least we know “the play’s the thing, wherein I’ll catch the conscience..”