Set a thief of catch a thief
Stealing things of others without their knowledge is a kind of art. Old and experienced thieves employ a lot of specialized tricks and techniques in stealing others' property. They also pass through all kinds of hazards. All these skills are unknown to people who are not thieves. In the same way, picking others' pockets has in our time been elevated to the level of fine art. One cannot know how his pocket was picked while getting into a bus or train or in a crowd. If one is a victim of theft and he wants to catch the thief he has to engage another thief for this purpose because a thief only knows the secret art of another thief. When one's foot is pricked by a thorn he has to use another thorn to remove it. Hence, to defeat a culprit of a certain kind one has to employ another culprit of the same kind.
