Depth refers to "seeing the ground", depending on whether the viewpoint is original or not, whether the materials cited to confirm the viewpoint can support this textual research, and whether the inference after textual research can stand scrutiny at several levels.

The breadth is big or small, and the small breadth is how many materials (preferably authoritative materials) are cited; Broadness is basically the cited materials, as well as the arguments and contents of your thesis, how many fields are involved and how long the time span is.