Abstract: We give an abstract paradox in mathematical language. Let F be a bijection from set A to set B. Denote M=a∈A|aF∉(a). If in a theory that M∈B is legitimate (or reasonable), then the question m∈M? becomes a paradox in that theory. This abstract paradox also can be regarded as unified schema for all paradoxes we have hnown. To get various concrete paradoxes we only need to give sets A, B and map F proper explanation. From the unified schema we find the common essential cause of all paradoxes, which creates a premise to solve the paradox problem satisfactorily.