The Trinity

Today's discussion centered around the doctrine of the Trinity. These three truths are central to understanding the Trinity:

1. God is three persons
2. Each person is fully God
3. There is one God

While it is hard to understand this in our limited minds, we do have several verses from scripture that clarify it. However, there are some teachings that deny one or all three of the above principles:

Modalism- There is one God that operates in three modes, much the same as a person that is sometimes a firefighter, sometimes a father, and sometimes a husband. Depending on the situation, he acts in a different role, but always the same person. The problem with this is that it denies that each person is fully God within the trinity and that God is made up of three persons.

Arianism- God the Father created the Son and the Holy Spirit. They are God, but not the same as the Father. They are subordinate to Him. This denies the equality of the Godhead and that there is only one God.

Although several illustrations fall short of describing the Trinity (the egg, water, partitioned harddrive, etc.), the one we discussed seemed to help me a lot.

The Trinity Shield

P= pater (Father) SS= spiritus sanctus (Holy Spirit) F= filius (Son)

non est = is not est = is

The Father is not the Son, the Son is not the Holy Spirit, and the Holy Spirit is not the Father

But all are God

Questions for discussion:
If understanding the Trinity is so important, why doesn't scripture spend more time unpacking this doctrine?

Is a proper understanding of the Trinity essential to being a believer? Can someone be a believer and not understand the Trinity as defined above?