The whole human cognition activity is how to explain and solve the practical problems encountered in the process of human survival and reproduction.By analyzing the famous cognition cases from ancient times to the present,four basic modes of human cognition are summarized as memory-driven experience mode(OOA),knowledge-driven reasoning mode(OODA),association-driven creation mode(OOCA),and hypothesis-driven discovery mode(OOHA).These four relatively independent cognition modes are used to formalize cognition.OOA and OOCA are bottom-up,shifting from physical space to cognitive space,while OODA and OOHA are top-down,shifting from cognitive space to physical space.The occurrence frequency of the four modes is different,and the transition between them is uncertain,which together constitute an endless cognition tending to be unified.The cognition formalization lays the foundation for constructing a new generation of AI system architecture that is interactive,self-learning,and self-growing.