From: Most Sacred Heart Catholic Church - Eureka, MO
The inscription reads "Pater non est Filius non est Spiritus non est Pater," and "Pater est Deus, Filius est Deus, and Spiritus est Deus." This is a graphical representation of the unity of our Trinitarian God—the Father is not the Son is not the Spirit... but all three are God. Three persons in one God.