Hamlet: O God, I could be bounded in a nut shell and count myself a king of infinite space, were it not that I have bad dreams.
Guildenstern: Which dreams indeed are ambition, for the very substance of the ambitious is merely the shadow of a dream.
Hamlet: A dream itself is but a shadow.
Rozencrantz: I hold ambition of so airy and light a quality that it is but a shadow's shadow.
[Act II, Scene II, Lines 270 - 278]