The Doctrine of the Trinity
Scripture provides two truth statements concerning who God is: “There is only one God” and “That one God exists in three persons, the Father, the Son, and the Holy Spirit”. These two statements appear to contradict each other, but they do not contradict. This is called a paradox. If the teaching is expressed as God is one, but not one; God is three, but not three, then this would be contradictory teaching, because one must be one. One cannot not be one! Three must be three. Three cannot not be three!
There isn’t a contradiction with the Trinity because essentially it is taught that God is one “what” and three “who’s”. The “what” is the divine substance, or essence, of God. Substance is the deity. There are three persons, the Father, the Son, and the Holy Spirit, who are one in substance. It could be expressed as saying that God is one (one divine substance) in three persons. The word person does not refer to being human either. Person simply refers to someone, not something, who is distinct and recognizable with a self-conscious, able to think and act on his own. It is with this understanding of “person” that the doctrine of the Trinity states that God is three in person and in substance.
The following video helps to illustrate this doctrine with citations to many verses from the Bible.