The Duke's schemes are developed more fully, and here we really see him directing his followers according to precise instructions. He tells Isabella and Mariana what to do with assuredness, although the plan could clearly fail, considering the intimacy of the proposed contact between Angelo and Mariana. The issue is not discussed clearly, nor is the question of why it is legal for the act to take place truly explored. After all, Claudio and Juliet had a similar contract of marriage to Angelo and Mariana's, and in that case both were willing. Here only one party is willing, and yet it is considered lawful. Perhaps it is the thought of tricking Angelo which makes the scheme seem appropriate here.
Mariana, when asked if she approves, answers that she will carry out the scheme if the friar thinks it is all right. The Duke assumed all along that Mariana would be willing to have sexual intercourse with Angelo, despite his hateful behavior towards her. The suggestion is that she can be redeemed only through this sexual act, because otherwise she remains a discarded woman instead of a wife.
The Duke also arranges a scheme involving the provost and the executions which are to take place. He is willing to sacrifice the life of Barnadine but wishes to preserve the life of Angelo. This implies a value judgment on life itself; one life is seen as worthwhile while the other is not. These statements of balance and equality figure largely in the play as a whole, as prospects are weighed against each other. The whole concept of "Measure still for Measure" (IV.i.414) centers around appropriate punishments and retributions.