Pneumatolgy, the theology of the Holy Spirit, is possibly the least known and appreciated of Catholic subjects of study. Knowledge of the Holy Spirit, sent into the world at Pentecost, is often lost in the concentration on the Father and the Son. For some, however, the Spirit of God is integral to guide them toward Christ and eternal life. A study of Catholicism must include an overview of the theology of the Third Person of the Trinity and the special gifts the Spirit brings to humankind.