Many Independent Catholic clergy are "essentially alone in their priestly practice" and exercise a primarily solitary vocation, with many of their family members and friends not even knowing of their clerical status. In line with Jesus' command to pray to God in secret and with the monastic tradition of hermit priests (e.g., Catholic Carthusians) praying alone but in mystical union with the entire church and interceding for the entire world, much of their worship is performed in private. Plummer suggests: "A growing number of clergy are comfortable with private celebration, when a community is not available, or if they have discerned that their vocation is largely a hidden one...Private celebration is often grounded in a deep conviction of the objective reality and efficacy of the sacraments. From such a perspective, even a mass said in one's living room unknown to any other soul, is still a radiant gift to the world, and a powerful prayer for those held in mind and heart. On a less exalted level, private masses for those without a community enforce one's priestly identity, which may be outwardly expressed in less obvious ways." Practically speaking, Plummer says, "viable independent communities are not always easily created, and these clergy would deprive themselves of the benefits of communion, and of the joining of themselves to Christ in his sacrifice, if they waited for the presence of others in order to approach the altar." When engaged in ministry with others, Independent Catholic priests often see themselves as missionaries, freely sharing the grace of the Church's sacraments with those who may not regularly participate in a church community.