The Trinity is the term that Christian theology uses to denote the tripersonal nature of God. Christian teaching asserts that there is only one God, but that this God exists in three persons: Father, Son, and Holy Spirit. These are not three different ways of talking about God, three different modalities of God, or three ways of God existing or appearing in the world; rather, they are three really distinct persons within the divine essence. The truth of the Trinity is not something that could be reasoned to, but rather is necessarily revealed to humanity. Christian teaching asserts that the existence of God is something that can be known by reason alone, but that it is only Jesus Christ who reveals the Trinitarian nature of God by giving humanity knowledge of the Father and the Holy Spirit.

The Incarnation is the term that denotes Christian teaching concerning the second person of the Trinity, the Word, coming to earth in human form. The term literally means “enfleshment,” which aptly describes the event in which the Son of God comes to earth in the person of Jesus Christ. The teaching on the Incarnation is one of the most essential truths of the Christian faith because it is the means by which the human race is redeemed from sin and elevated to the life of grace and communion with the Trinity.