Here are some of my posts regarding the doctrine of the trinity:
History of the Doctrine of the Trinity,
What is the doctrine of the Trinity?,
Trinity = Three Persons in One God,
Trinity using Bible words, trying to reconcile with theological terms,
IS the Holy Spirit separate from God the Father or God the Son?,
Is Christ God?,
Did Jesus exist before time? Is Jesus God?,
Is the relationship between God the Father and Christ supposed to be familial?
Did the Apostles mention the Holy Spirit as a separate person?,
Is Christ the Spirit of Truth?
