The dialogue of the first part of the scene reveals that Macbeth has met the murderers before. Both then and now, he must convince them to work on his behalf. Whether true or not (we have no evidence), he kindles, or re-kindles, in them, a hatred of Banquo: "Know that it was he . . . ," "This I made good to you in our last conference," "Do you find your patience so predominant in your nature that you can let this go?" The tone of these quotations is more than simply interrogative; Macbeth must ensure that the men are not persuaded by the slightest moral scruple, the slightest sympathy for Banquo, to betray the plan. Such a reaction would be entirely natural and human, but that humanity is precisely what Macbeth cannot now allow. Therefore, when the First Murderer replies, "We are men, my liege," Macbeth cuts off his speech and, in a sequence of powerful metaphors, reduces the humanity of these murderers to the level of beasts: "Ay, in the catalogue ye go for men, / As hounds and greyhounds, mongrels, spaniels, curs / . . . and demi-wolves are clept [called] / All by the name of dogs" (93-96).
Although Macbeth flatters the Murderers by suggesting that the business of Banquo's murder will elevate them above the common rank, his ironic tone reveals that he thinks of them as little more than beasts. Doubly ironic, then, is that this entire speech is admission to himself of his own inhumanity and imperfection: Macbeth himself is acting like a "demi-wolf." The lines are triply ironic when we see that indeed the murderers are, themselves, imperfect in carrying out his instructions for the "perfect" crime.
This notion of perfection is one that now comes to dominate Macbeth's thoughts. Banquo's death would make Macbeth's "health . . . perfect"; and the crime must be committed at "the perfect'st spy of the time" (the exact hour). Both of these quotations foreshadow Macbeth's line in Act III, Scene 4, when, hearing of the botched attempt to kill Fleance, he remarks "I had else been perfect." The tragic assumption that one can commit a perfect crime and escape the consequences is about to be tested.
As if to impress us with the connection between the killing of the king (the blame for which could, after all, be laid at the door of Fate) and the killing of Banquo (blame for which most definitely cannot), the final couplet ("It is concluded: Banquo, they soul's flight, / If it find heaven, must find it out tonight") ironically recalls the words spoken by Macbeth immediately prior to his killing of King Duncan: "Hear it not Duncan, for it is a bell / That summons thee to Heaven, or to Hell."
verities (8) true predictions
parricide (31) murder of a parent
rebuked (55) mocked
fil'd my mind (64) defiled my guiltless conscience
rancours (66) bitterness
eternal jewel (67) immortal soul
Enemy of Man (68) the Devil
list (70) tournament
utterance (71) utmost
probation (79) approval
borne in hand . . . cross'd (79) deceived, double-crossed
half a soul (82) a half-wit
shoughs, water-rugs (93) rough-coated dogs
particular addition (99) a specific title
avouch (119) justify