Tong 同 and its associated concepts such as datong( great tong 大同) and( xuantong mystic or dark tong 玄同), have played significant roles in the development of Chinese philosophy. Yet the concept of tong has received little attention from either western or eastern scholarships. Tong is also widely understood as "sameness" or "unity". Based on a definition of this concept in The Mohist Canon ,we can reach a new understanding of it that is " difference to one" . This understanding can be supported from etymological and textual evidence. "Difference to one" should not be solely attributed to a Mohist understanding it does represent a common understanding across philosophical streams in early China. "Difference to one" provides new insights into the concept of tong in early philosophical texts breaking new ground for further studies of tong and its associated concepts.