do scholars know the purpose, on a meta level, of the third murderer in macbeth? i've read theories that it's macbeth himself, but that's never stated... but having a random third assassin show up feels almost unnecessary?
This is one of those textual things people love to develop theories about and that theatrical companies like to exploit to try and add a twist. People have suggested, as you say, that it’s Macbeth himself, or that it’s Ross or Destiny... I’ve seen directors who have chosen to cast Seyton in the role in many theatre performances, no doubt partly because there is that Seyton/Satan homophone that’s so very tempting.
But as you say, it’s never stated, and if it was Macbeth or Ross, or any named character, it’s quite unlikely that it would go unmentioned because Shakespeare tends to be explicit about that kind of thing (when someone is in disguise). Nicholas Brooke, the editor of the Oxford edition is pretty dismissive, saying that ‘Speculation about the identity of the Third Murderer... is absurd’. His argument is that the opening lined when the first two murderers ask, ‘But who did bid thee join with us?’ and the Third Murderer replies, ‘Macbeth’ is sufficient to explain his presence. The Arden editors ( Sandra Clark and Pamela Mason) are less dismissive but agree that it makes enough dramatic sense because ‘as Dover Wilson says, the introduction of a further assassin shows that Macbeth, “tyrant-like, feels he must spy even upon his own chosen instruments”’. Given the overall paranoid feeling of the play at this point, I find this pretty convincing, and even if it’s not staged, you can imagine Macbeth having even more doubts and sending a spy to join the murderers.
For the sake of the murder itself, the Third Murderer is not necessary, as you say, but there is something dramatically effective about having this other figure who’s not really acquainted with the other two. It means, for one thing, that when one of the other murderers (most likely the First Murderer) strikes out the light, the Third Murderer is not on board with it and can accuse the other two of messing up the assassination. This is quite a typically Shakespearean technique: he introduces a little bit of a dynamic even between minor characters to create drama.
The presence of the Third Murderer is definitely something that theatre directors will continue to exploit to their advantage, and there are no doubt scholars who have investments in particular interpretations. Still, the general consensus is that there’s not much mystery here as the text provides a sufficiently convincing reason for the Third Murderer to be present.
