Just as powerful men have struggled for supreme power in the previous scene, here you see the struggle of men as they fall out of love. (It is important to remember that when male Shakespearean characters speak of love, they mean friendship.) Note the type of passionate language used to describe how Brutus and Cassius feel. Brutus says, "Thou hast describ'd / A hot friend cooling. Ever note, Lucilius, / When love begins to sicken and decay / It useth an enforced ceremony." In addition, the imagery of sickness and decay in this quote underscores the potential destructiveness of emotion. The question of how to reconcile passion and reason — the mind and the body — are ultimately unresolved.
Note that this scene stands in contrast to the previous scene, especially in the use of horse imagery. In the previous scene, Antony speaks of Lepidus as a horse as a way of indicating the latter's inferior position. Here, Brutus denounces Cassius as a hollow man, who like a horse "hot at hand, / Make[s] gallant show and promise of [his] mettle." Antony's use of the imagery indicates control; Brutus', a loss of control.
