The term xin (心), usually translated as “mind,” “heart” or “heartmind,” is considered a major problématique in traditional Chinese philosophical discourse, and it is usually analized in conjunction with xing (性, human nature). Contemporary scholars consider xin—more or less uncontroversially—as a sort of container of emotions and feelings, or, as On-Cho Ng defines it, “the very home of volition, sentiments and intellect” (Ng 1999). This paper aims to further explore the impact of the physiology of heart (xin) rhetoric within political discourse during the early decades of the Western Han dynasty (206 BC-AD 9). To that end I will first analyze the importance of physiological vocabulary in political argumentation, focusing mainly on the importance of heart (xin), its central role as the ruler of the body, and on the analogy between the heart and the sovereign of the state. I will then analyze the use of the expressions unanimity and duplicity—literally, pitting one heart (yixin 一心) against two hearts (erxin 二心 or liangxin 兩心).