大乘義章 1.36

1.36

佛性義五門五別（釋名一　辨體二　料簡有無內外三世當現之義三　明因義四　就性所以五）

The meaning of Buddha-nature has five sections with five distinctions: 1. Explaining the Name; 2. Differentiating the Essence; 3. Examining the meanings of existence and non-existence, internal and external, the three times, and future versus present; 4. Clarifying the meaning of causes; 5. Examining the rationale for "nature".