Barbara Tovey, "The Golden Casket: An Interpretation of The Merchant of Venice," in Shakespeare as Political Thinker, eds. Alvis and West, 261–87

Excerpt:

The teaching that appearance often belies reality figures prominently in many Shakespearean plays. It seems fair to say, however, that there is no play in which that teaching is given such frequent explicit utterance as The Merchant of Venice. Measure for Measure is the only possible rival. In that play there are at least two characters who concretely embody the appearance-reality antithesis. Angelo seems virtuous but is not. The Duke, applying craft against vice, disguises himself as a friar. Contrary to what one might expect, in The Merchant there does not seem to be any character who exemplifies the principle that “outward shows” are least themselves.

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