The nembutsu of the fundamental vow can and should be truly independent, for it requires no external supports. By "external supports" I mean reliance upon one's human intelligence, moral conduct, the heart that seeks the path, compassion, or anything else. None of these is an auxiliary to nembutsu, which stands alone.
Good people should seek salvation in the recitation of "Namu Amida Butsu" just as they are. And bad people should seek salvation in "Namu Amida Butsu" just as they are. Whether they are bad or good, let people just recite "Namu Amida Butsu" as they were the day they were born. Such a person need not depend on any other means. Even so, every one who tries to rectify his evil ways, and do good deeds, acts in accord with the Buddha's wishes.
If a person's mind is not set on going for birth, or if he believes himself to be disqualified for this reason or that, then his birth in the pure land is not assured.
~ Hōnen Shonin (1133-1212)
(Gyojo ezu, Chapter 21).