The reason for composing a public theory of the legal ability is to reveal the common rules, that all its dispersed applications contribute to all civil law's items. The ability with its different applications has one origin, determination and one foundation. The importance of composing one public theory relied on many legal patterns, many options and the granting given by law to specific persons regarding their positions, and they can be called the legal abilities, which made us confronting responsibility in presenting answers for the questions that will be asked: What we mean by legal ability? What is its statutory basic? What are its conditions, content and applications at the civil legislation? And many other general questions. Regarding this study, all the questions will be answered.