In the high middle ages, various kinds of popular religious movements prevailed all over Western Europe. Their, religious piety has subjective and individual character in opposition to the objective and collective devotion which was common to the faithful of the early medieval church. Most of those popular religious movements had not been accepted by the Catholic church and so they become heresies. St. Francis of Assisi and his desciples appeared in the midst of those popular religious movements and they had also in common subjective and individual piety. But why did St. Francis and his followers remain in the Catholic church, while the other religious movements were regarded, as heresies ? The answer to this question is in this article. And in conclusions, St. Francis' intense subjective piety had strong connection with reverence for the human nature of Christ. The body of Christ has its real presence in the holy hostia reposed in the church. Therefore, St. Francis regarded the visible church as the custodian of the holy hostia and held it in great reverence. In this way, St. Francis was never expelled by the church and remained in it.