Sebastian is nearly convinced, but he asks, “But for your conscience” (271). Sebastian is asking about guilt. He is asking Antonio how he dealt with the feeling of guilt after he had usurped the position of power from Prospero.
Antonio explains the idea of conscience and guilt through two metaphors: a kibe (line 272) and candy (line 275). Antonio is asserting that conscience or guilt is like a kibe (an inflammation or sore that occurs on the foot from cold moisture). Such a sore may be inconvenient and force the sufferer to wear soft slippers instead of boots. However, Antonio is declaring that guilt (like a kibe) does not affect the heart or spirit of a man. And just as a kibe will eventually go away, so too will any feelings of guilt. Guilt, according to Antonio, is only a temporary inconvenience. The metaphor to sugar candy (or rock candy: sugar in hard crystal form) also suggests that conscience is only a temporary inconvenience. Such candy dissolves or melts as soon as one places it in his mouth. The hardness is not really an obstacle. Thus Antonio implies that conscience is not really an obstacle either. However, Shakespeare is implying that some men, like Antonio, really have no conscience at all.
Antonio then draws his sword to kill King Alonso while Sebastian draws his sword to kill Gonzalo (mockingly referred to as Sir Prudence in line 282). Antonio tells Sebastian not to worry about the two lesser lords (Adrian and Francisco) since they will believe any story that Antonio will tell them.
Ariel, however, arrives in time to save Alonso and Gonzalo. The airy spirit comments that Prospero had predicted or foreseen the danger (line 293). Foreknowledge, the ability to see future events, is a quality often attributed to God; and Prospero is often godlike in his abilities and powers.
Ariel thus awakens Gonzalo and King Alonso. Alonso asks Antonio and Sebastian why they have their swords drawn, but the crafty Sebastian quickly responds that they heard the roaring of some large, wild animal, like a lion.
Alonso accepts Sebastian’s explanation, and the group of men goes off on a search for Ferdinand, the king’s son.