 The content of the texts is roughly coherent but not tightly so. The concepts and theories presented generally fit together well, with variations in terminology. But the organization of the texts is unsystematic. There is no statement of their overall purpose, no clear organizational scheme, nor any headings indicating the themes of different  parts.[3]  The canons do tend to fall into thematic groups, such as series on knowledge, the virtues, geometry, or argumentation, but the sequence of topics displays no clear pattern. Concepts are introduced only to never be mentioned again, and central terms sometimes go unexplained. Like early Chinese mathematicians, the Mohists had no conception of an axiomatic system, and the canons do not clearly identify anything corresponding to axioms, definitions, or theorems. Nor are they arranged as if to explore a specified set of themes or prove some distinct set of conclusions. As a result, interpretation of later Mohist doctrines can be testing. They must be reconstructed from terse, incomplete statements scattered about different parts of the corpus, and on some issues there is insufficient textual evidence to reach any firm  conclusions.[4] 