In chapter 15, after Huck has played a mean trick on Jim and Jim calls him out for it, Huck says,
It was fifteen minutes before I could work myself up to go and humble myself to a nigger—but I done it, and I warn't ever sorry for it afterwards, neither.
Huck has recognized Jim's humanity. He understands that Jim sees him as a friend and that he has truly hurt Jim's feelings. Huck has to work hard to unlearn all the racial attitudes he has been surrounded with all his life.
Near the end of chapter 23, Huck witnesses Jim's grief in the early morning hours and intuits that Jim is "low and homesick" and likely thinking about his wife and children. Huck thinks,
...I do believe that he cared just as much for his people as white folks does for theirn. It don't seem natural, but I reckon it's so.
This observation is another indication that Huck sees Jim as a fellow human being and not someone lesser than himself or white people in general.
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