In the first scene of this act Macbeth dwells on the worthlessness of the mere title which he has won, “To be thus is nothing, but to be _safely_ thus.” Then, too, the succession was promised to the issue of Banquo, leaving a barren sceptre in the hands of Macbeth. He resolves to have the substantial prize for which he had “filed his mind,” and therefore plans the destruction of Banquo and Fleance. In the conversation with the murderers whom he engages for that purpose, the theme is curiously illustrated. In reply to Macbeth’s question as to their readiness to revenge an injury, they say, “We are men, my lord.” _Macbeth._ Ay, in the catalogue, you go for men As hounds, and grey-hounds, mongrels, spaniels, curs, Shoughs, water-rugs, and demi-wolves are clep’d All by the name of dogs; the valued file Distinguishes the swift, the slow, the subtle, The house-keeper, the hunter, every one According to the gift which bounteous nature Hath in him closed. The _ambiguity_ of the general name is remedied by the _specific_ description. The name is _formal_, the description _substantial_. In the next Scene (the 2d) both Macbeth and Lady Macbeth continue their reflections on the insecurity of their usurped honors: “We have scotched the snake, not killed it.” She exhorts him to “sleek o’er his rugged look;” and he refuses to explain his purposes as to Banquo, bidding her be innocent of the knowledge till she can applaud the deed; thus sparing her conscience the _formal_ guilt of the murder. His invocation to night and darkness, at the end of this scene, is very similar to that of Lady Macbeth, on a similar occasion, before referred to. In the 3d Scene the murderers, whilst waiting the approach of Banquo, justify to themselves the deed they are about to commit, by pleading the orders of Macbeth. The deed is his; they are the mere instruments of his will. The allusion to the fading light; “the west yet glimmers with some streaks of day,” seems to refer to the near approach of Banquo’s end; as the extinguishment of the light does to the simultaneous extinguishment of his life, immediately afterward.