Like Musashi, students of Ni Ten Ryu find themselves studying the ways of many other "schools" (or styles). Musashi writes of the problems he saw within many of the other schools, yet he maintained that without this knowledge one could not fully understand his Heiho or way.
Musashi, like his contemporaries, was heavily influenced by Zen philosophy. This philosophy or "way of looking at life", holds that a teacher cannot teach understanding. A teacher can merely lead the student to their own enlightenment. This approach runs through Go Rin No Sho, Musashi repeatedly writes of things as "self evident", or states that a sudent must learn certain things for themselves.
An understanding of other schools or styles helps one not only in combat against someone using such a style, but also to more objectively review ones own way, perhaps even adopting a better technique.