This weekend we celebrate the Trinity. That is, we celebrate the Catholic faith in substance, what the Catechism calls the “central mystery,” the dogma without which we are nothing, without which there is no salvation—our faith that there is “only one God, the almighty Father, his only Son, and the Holy Spirit.”

Encountering Jesus, the disciples knew he was one with the Father, that what they said and believed of the Holy One of Israel, they now said and believed of Jesus. This is the scandal of the incarnation, that the Word became flesh and dwelt among us. And, of course, Jesus spoke of the Spirit. The Spirit is the gift of the Father and the Son, and he will lead us and keep us in truth. The Spirit descended on Pentecost and dwells among us still. Father, Son, Holy Spirit—Trinity. This is all the word means, naming how God dwells among us and saves us.

Don’t be intimidated by the dogma of the Trinity. It’s got a complex history, but it’s actually simple. It’s also essential, so don’t neglect it. It’s what makes Christianity distinct. And it’s what keeps our faith from becoming mere bland moralism. Because it reminds us of divine depths and destiny—mine and yours.