According to Pentecostals, all manifestations of the Spirit are to be judged by the church. This is made possible, in part, by the gift of discerning of spirits, which is the capacity for discerning the source of a spiritual manifestation—whether from the Holy Spirit, an evil spirit, or from the human spirit. While Pentecostals believe in the current operation of all the spiritual gifts within the church, their teaching on some of these gifts has generated more controversy and interest than others. There are different ways in which the gifts have been grouped. W. R. Jones suggests three categories, illumination (Word of Wisdom, word of knowledge, discerning of spirits), action (Faith, working of miracles and gifts of healings) and communication (Prophecy, tongues and interpretation of tongues). Duffield and Van Cleave use two categories: the vocal and the power gifts.