Final answer:
The statement that the Trinity is the doctrine that the Father, the Son, and the Holy Spirit are one God is true, as this is a central belief in Christian orthodoxy that emerged in the early centuries of theology.
Step-by-step explanation:
The doctrine of the Trinity holds that God the Father, God the Son (Jesus Christ), and the Holy Spirit are three distinct persons in one God. This foundational Christian belief asserts that each person of the Trinity is God, whole and entire, and yet there is but one God. This doctrine emerged during the second and third centuries as theologians attempted to reconcile the oneness of God with the scriptural references to the Father, the Son, and the Holy Spirit. Despite being one of the central aspects of Christian orthodoxy, the concept of the Trinity has been a point of contention, inspiring theological debate and even leading to accusations of heresy among different Christian groups.
Therefore, the statement that the Trinity is the doctrine that the Father, the Son, and the Holy Spirit are one God is true.