Prof. Dr Johannes van Oort, Professor Extraordinarius in the Department of Church History and Church Polity of the Faculty of Theology at the University of Pretoria, South Africa, adds that, in addition to praying for wisdom, the early church was very much involved with different charismas, one of which being healing. Praying for other people's illnesses was another way that intercessory prayer was important in the early church, as healing was a sign of "the power of God's Kingdom". This gift of healing is specifically mentioned, among the other charismata, as a sign of being a true Christian by Irenaeus of Lyons in his text, "Against Heresies".