Athanasian Creed

"Even if Catholics faithful to Tradition are reduced to a handful, they are the ones who are the true Church of Jesus Christ."

• My annotated version of the Athanasian Creed.
• Translation by the Reformed Church.

Shield of the Trinity

From Wikipedia's article on the Athanasian Creed:

For those who lack Latin:

• Pater = Father
• Filius = Son
• Spiritus Sanctus = Holy Spirit
• Deus = God

"Est" means "is."

"Non est" means "is not."

So the symbol contains all of these sentences:

The Father is God. The Son is God. The Holy Spirit is God.

The Father is not the Son. The Father is not the Holy Spirit.

The Son is not the Father. The Son is not the Holy Spirit.

The Spirit is not the Father. The Spirit is not the Son.

The diagram implicitly presents the doctrine of the Trinity: there are three Persons in one God.