"Is this a dagger which I see before me, The handle toward my hand? Come, let me clutch thee: I have thee not, and yet I see thee still. Art...

At this point in the play, Lady Macbeth has persuaded her thane husband to commit regicide, but he's still reticent to do it. He's still a good man, albeit one who is considering throwing his life, his honor, his name, and his soul to the devil, all for the sake of the crown. He's waiting for Lady Macbeth's signal that everything is ready for him to walk into Duncan's chamber and murder the king (she...

At this point in the play, Lady Macbeth has persuaded her thane husband to commit regicide, but he's still reticent to do it. He's still a good man, albeit one who is considering throwing his life, his honor, his name, and his soul to the devil, all for the sake of the crown. He's waiting for Lady Macbeth's signal that everything is ready for him to walk into Duncan's chamber and murder the king (she is drugging the grooms/guards). He's having his first "fit" at this point--seeing things that aren't there. It's a sign of things to come (when he sees Banquo's ghost at the banquet and thereafter becomes more and more erratic and paranoid). Here, he realizes that his mind is playing tricks on him--that he isn't all there, that something's wrong with the plan, but he proceeds with it, anyway.