需要是实践活动的动因 ,主体的“需要结构”把实践活动区分为历时性的四个阶段 ,社会作为主体的存在方式 ,又把实践活动的四个阶段转换为共时性的四个类型 ,即探索实践、创造实践、变革实践和生产实践。不同类型的实践活动有不同的目的 ,主体目的规定了实践活动类型的性质、特点和作用 ,形成主体和客体的阶段性特征 Necessity is the motivation of the practical activities. The “Necessary structure” of the subject divides the practical activities into four stages of diachronicity, the existence mode of the society as the main body, and the four stages of the practical activities into four types of synchronicity. That is to explore practice, create practice, change practice and production practice. Different types of practical activities have different purposes, the main purpose of the provisions of the nature of the types of activities, features and functions, the formation of the main characteristics of the stage and the object