He feels strongly about preserving and maintaining them.
Explanation:
In this excerpt, Joseph is willing to continue whith his tribe's cultural tradition: to regain their lands from the hands of the white. Joseph's father has just died without being able to regain his land in Oregon. As a consequence, Joseph feels stronger in preserving and maintainnig their resistance against the white. "<em>He left a good name on earth. He advised me well for my peopl</em>e" these words make Joseph's intentions clear: he will go on with the tribe's peaceful fight against the white.
I'm pretty sure it is Theme. Theme is the central topic of the text. passage, story, or anything else. So it may possibly also be the same for the underlying meaning and universal truth...but again, I am not sure.
