Catechism of the Catholic Church

"Now this is the Catholic faith: We worship one God in the Trinity and the Trinity in unity, without either confusing the persons or dividing the substance; for the person of the Father is one, the Son's is another, the Holy Spirit's another; but the Godhead of the Father, Son, and Holy Spirit is one, their glory equal, their majesty coeternal" (Athanasian Creed; DS 75; ND 16).