When you know what a man wants, you know who he is, and how to move him.

The line distills a hard-edged view of human motivation: desire is the most reliable key to character and the most effective lever for influence. It suggests that ideals, loyalties, and even stated principles often matter less than what someone privately hungers for—power, love, safety, recognition, revenge. Once that want is identified, a person becomes predictable: you can anticipate choices, bargains, and betrayals, and you can “move” them by offering, threatening, or manipulating access to the object of desire. The quote’s significance lies in its political realism, treating interpersonal and institutional power as the art of reading and exploiting incentives rather than appealing to virtue.