In this scene we hear how the doctor cannot heal Lady Macbeth. He says that she is ‘troubled with thick-coming fancies’ (line 38). This applies equally to Macbeth, who starts and ends the scene by talking about the prophecies which in themselves can be seen as ‘fancies’. He has chosen to believe them and live his life according to them. Like his wife, he is obsessed. He rejects the doctor’s advice about healing, with ‘I’ll none of it’. Instead his restless energy seeks violent outlets - the casual way he orders the hanging of anyone talking of fear (line 36) shows how callous and depraved he has become. Examine another part of the play where healing is referred to and compare with this one. You might look at Act IV Scene 3 where the Doctor explains how the King of England seems to have a miraculous healing touch.