An excellent source on the cultural context applicable to Shakespeare's work is E. M. W. Tillyard's The Elizabethan World Picture. Use this as a supplement to our discussion of the "Great Chain of Being" as it relates to The Merchant of Venice. You might also consider Wikipedia's entry on usury. And if you want to revisit the language of commerce, love, and vengeance, consider the brilliant film by Jane Campion, The Piano.