Read the excerpt from Romeo and Juliet. Romeo: "Peace, peace, Mercutio, peace! - Thou talk'st of nothing." Mercutio: "True, I talk of dreams, - Which are the children of an idle brain, - Begot of nothing but vain fantasy, - Which is as thin of substance as the air - And more inconstant than the wind". What kind of dreams is Mercutio describing, especially when he calls them "Children of an idle brain"?

Mercutio is describing imaginary or unrealistic dreams, which he refers to as "the children of an idle brain." By using this phrase, he suggests that these dreams are unproductive and originate from thoughts that lack purpose or importance. In other words, Mercutio believes that these dreams are the result of idle or idle-minded thinking, devoid of any substantial substance or value.