Why do some critics claim that Shakespeare did not write Act 3 Scene 5 of 'Macbeth'?

Answer 1

There was a lot of rhyming which Shakespeare only used when ending an act or when the witches were casting a spell. Hecate is not casting a spell but still rhymes throughout her monologue. The witches speak in iambic tetrameter not iambic pentameter. The witches are not portentous but silly fairies like the fairies in Midsummer Night's Dream, which does not match their appearance in Act 1. And here's the clincher: two of the songs they are supposed to sing and dance around to are known to have been written, not by Shakespeare, but by Thomas Middleton, who used them in his own play The Witch, which was written some ten years after Macbeth. It is thought that Middleton, who was working for the King's Men at the time, was asked to tart up this old play by the addition of some new scenes and dialogue featuring Hecate, a character from The Witch. Act 3 Scene 5 and parts of Act 4 Scene 1 are the result.

Answer 2

Act 3 Scene 5 is almost certainly not by Shakespeare because it is not in his usual style, being in rhyming couplets in iambic tetrameter, because it is different in tone from the scenes with the other witches, because it contains a reference to a song "Come away, come away" which is actually by Middleton, and because it alters the witches' characters from the way they are portrayed elsewhere. Scholars think that this scene and parts of Act IV Scene 1 were added by Thomas Middleton in an attempt to make the play more commercial by making it into a musical and the witches more cutesy, along with a couple of Middleton's songs from his play The Witch.

Anyway everything to do with Hecate the Witch Queen is awful and she and all her songs and cutesy dances are regularly thrown out by directors. You will have a very difficult time finding a professional performance of this play in which any actress is cast in the part of Hecate. It is never done and 3,5 is never performed.