The nembutsu is said in gratitude and not to earn merit

In most Pure Land teaching current in Shinran's own lifetime, reciting Amida's name, the nembutsu, was understood as a practice performed to accumulate the cause of birth in the Pure Land, said with the intention that the saying itself contributes toward that outcome. Shinran's doctrine reverses the direction of that intention entirely: because shinjin alone, received as Amida's gift, already settles birth in the Pure Land at the moment it arises, the nembutsu recited afterward cannot be earning anything still outstanding, and Shinran states plainly in his own writing that the nembutsu is not a practice in the ordinary sense at all but the spontaneous expression of gratitude for a liberation already accomplished. This reordering changes what a lapse in recitation means within the tradition: where nembutsu understood as merit-earning practice would make missed or half-hearted recitation a mark against the practitioner's progress, nembutsu understood as gratitude carries no such accounting, since nothing was being earned by it in the first place. Dobbins' study of the school's formation notes that this distinction, between practice as cause and practice as thanksgiving, was among the doctrinal points that drew the sharpest criticism from rival Buddhist schools in Shinran's own century, who read his position as removing incentive for religious discipline even as Shinran's own account presented it as removing a subtly self-powered motive hidden inside apparently pious repetition.

Shinran's teacher Honen, who founded the independent Pure Land school Jodo Shu a generation before Shinran established what became Jodo Shinshu, had already taught that reciting Amida's name was the one practice suited to a degenerate age in which more demanding disciplines had become impractical, a position that itself broke sharply from the wider Buddhist establishment of his time. Shinran's doctrine that the nembutsu is gratitude rather than cause carries Honen's simplification a further step, and the two schools that trace to teacher and disciple have kept the difference visible ever since: Jodo Shu still generally treats sustained nembutsu recitation as itself contributing toward birth in the Pure Land, close to Honen's own teaching, while Jodo Shinshu's doctrinal center holds that shinjin alone, received once, already accomplishes what the recitation in Jodo Shu is understood to work toward gradually. Historians of the two schools' formation trace part of this divergence to the circumstances of Shinran's own exile, a punishment imposed on Honen's movement by the court in 1207 that scattered Honen's students and sent Shinran to the provinces as a laicized, married teacher outside the capital's monastic institutions, a setting in which the doctrine Shinran built could not assume the kind of sustained ritual discipline available to monastics closer to the center of institutional Buddhism.