Every Sunday Catholics around the world, whatever their differences in nationality, race, social status and gender, stand together to profess a common witness to the apostolic faith of the Church, the Nicene Creed. With one voice they proclaim: "We believe in one God the Father almighty, creator of heaven and earth. " How easy and straightforward that seems, yet within the Western theological tradition of the trinity, which lies at the heart of Catholic theology, this apparently simple statement is lacking clarity of which most Christians are completely unaware. Some of the lack of clarity is shown through a comparison with the Credo of the People of God written by Pope Paul VI, which begins with: "We believe in only one God, Father, Son and Spirit, creator. " The reasons for this change, from naming the Father as creator, to speaking of the one God, Father, Son and Spirit as creator, can be found in a rather big shift in thinking in Western theology. This notion had an experimental base. As full-fledged Jews, Jesus' disciples affirmed Yahweh unquestioningly . But as they came to see Christ as Yahweh's extension in the world, and as his life and mission gained clarity, they began to assimilate him to the define . This meant they could now apprehend God either directly or through his son. Then came Pentecost, and a third visitation. The disciples were all filled with the Holy Spirit. They vowed this even as the dramatic arrival of the third party, the Holy Spirit to the divine assembly . This marks a shift from an earlier stance, one that continued in the Eastern tradition, of beginning with God the Father as the source of all that is . Up until the 20th century, the writings of Augustine and Aquinas dominated the Western Catholic tradition. Like a stonewall they stood against the changing ideas of theological conflicts, presenting an apparently permanent achievement that withstood the arguments of every opponent.