He is presented as a loyal and heroic warrior who had no apparent lust for power. However, the flames of ambition could be seen when he uttered "tell me more" after the witches prophecy. The prophecy, however, is half finished and he is responsible for finishing it off himself. Thus, the main plot is set in motion and is a chilling foreshadowing of the influence of power and the corruption it has, even on a "good" person like Macbeth. Macbeth is seriously conflicted between a number of possibilities. He seriously considers letting fate take its course ("If chance would have me king, why then let chance crown me."), taking agressive action ("Prince of Cumberland! That is a step on which I must fall down or else o'erleap for in my way it lies."), and doing nothing and disregarding the prophecy ("We shall proceed no further in this business.") What drives him to commit the murder is not "vaulting ambition" but his fear that his wife will consider him less than manly.
