We are able to know certain eternal truths without the light of faith. According the Church for example, the greatest truth of all—God exists—is knowable from the light of human reason and the works of creation alone.
But there exist truths that we cannot discover until God reveals them to us. The doctrine of God as a Trinity of Divine Persons is an example of such a Divinely Revealed truth.
This is one of the most fundamental beliefs of Catholics, yet we are not…