James continues his discussion of partiality by showing in part why it is wrong. It is a failure to keep the entirety of the "royal law." Both the rich man and the poor man are the subjects of the law, "You shall love your neighbor as yourself." When they only practiced such toward the rich man they stumbled in one point and became a transgressor of the entire law. This leads into a discussion of faith that is "perfect," or complete - a faith with works. God wants us to be doers (1:22-25) of the entire word, applying it in every situation it is to be applied. We are not showing such faith if we pick and choose which laws to keep, nor are we when we pick and choose whether to apply a certain law in varying situations which demand application.