"Diamonds Cut Diamonds"
Context: Menaphon, a young gentleman of Cyprus, returns home after a year's travels, with a tale of having found a marvelously handsome and talented boy, Parthenophill, who has joined him as a companion. Menaphon is much in love with Thamasta, a cousin of the Prince of Cyprus and sister of Amethus, Menaphon's close friend. Thamasta, however, does not return Menaphon's love, and it was largely because of her coolness that he went on his travels. Menaphon calls on her, accompanied by a person purporting to be Parthenophill who is really the lady Eroclea in man's clothing. Thamasta falls in love with the supposed Parthenophill and confides in her maid Kala that she will win him by subterfuge. In her speech she uses the expression "diamonds cut diamonds," which plural form is as common as the modern singular "diamond cut diamond," although the singular form was also popular at an early time. Another form of the expression, also popular, is seen in John Webster's The Duchess of Malfi (1613-1614): "Like diamonds we are cut with our own dust." The expression means that it takes cleverness to combat cleverness, much like the popular, "Set a thief to catch a thief." Thamasta's speech is:
. . . Whilst we striveTo live most free, we're caught in our own toils.Diamonds cut diamonds: they who will proveTo live most free, we're caught in our own toils.