This paper investigates the Coleridge-Southey dialogue about their dramatic works of The Fall of Robespierre and Wat Tyler in 1794. By concentrating on the three ideas of "virtue", "justice" and "vengeance" found in both plays, this paper proposes a possibility of tracing poetic dialogue between Coleridge and Southey and shows how the dialogue continues as responses to previous poems. During the composition process in The Fall of Robespierre, Coleridge recognized differences in the essential concepts of virtue and justice between him and Southey, and supplemented reoriented concepts of virtue and justice, denial of justification of genocide, in order to respond to Southey's part of the play. Southey, in turn, was discontented with ideologies of the French Revolution expressed in their own drama of The Fall of Robespierre. Southey reorganized the ideas of justice and vengeance according to his own liberal-radical politics and demonstrated them in the similar theme of Wat Tyler in order to respond to his and Coleridge's previous play The Fall of Robespierre. Thus this paper shows how the Coleridge-Southey poetic dialogue was carried out in the collaborative composition of The Fall of