Who is the Holy Spirit? What role does the Spirit play in the life of the Church and of the individual Christian? Beginning with the belief in the Holy Spirit as a Person of God, and not just a "force," this book reveals the Catholic understanding of the presence and influence of the Spirit God in every aspect of the Christian life. The book focuses on the unique aspects and development of Catholic devotion to the Holy Spirit from antiquity to the present, culminating in a look at Catholic theology of the Holy Spirit today and the new and exciting ways the Spirit is working among Catholics and all Christians in the 20th and 21st centuries.