Where Is The Inciting Incident In Hamlet?

The inciting incident in Hamlet is up for much discussion.  Some believe it is Old Hamlet's ghost visiting young Hamlet on the battlements, but some believe that it occurs before this, when Claudius kills Old Hamlet.

I believe that the inciting incident, which is the event which sets the entire play off is actually Old Hamlet on the battlements, because I believe that whilst the play does exist to some extent in the antecedent events prior to the beginning of the play, there is always an inciting incident inside the play itself, at some point, something happens to get the characters going on their date with destiny, which draws them towards the conclusion of the play and in our case, (well Hamlet's actually), death.

Robert McKee believes that Hamlet is a Whodunnit and they have two part inciting incidents, but I think he's covering up for not thinking his answer through!