The trinity

Soon I will begin a two or three part series of posts on modern challenges to the doctrine of the trinity from pseudo-Christian groups.
I was raised in a church that denied the trinity. It taught a variant of what is commonly known as "Oneness theology," and also goes by the tag line "Jesus Only." You find it mostly in various strains of pentecostalism, most prominently in the United Pentecostal Church, which was once a part of the Assemblies of God (and in fact, broke from the Assemblies over the trinity).
This doctrine of the trinity typically comes under the most attack by cults. In fact, it is usually the last thing a cult victim can grasp. They may come to terms with other false doctrines and find the truth, but they will often remain blind to the essential nature of God, and even, upon leaving the cult, will refuse to go to an evangelical church because, "They seem all right in everything else, but they're trinitarians."
It is thus incumbent of every Christian to have a working knowledge of this doctrine. And I think it is helpful to understand how and why the doctrine comes under attack. When you study the issues and the "seed" of oneness theology, you see that the various components go back hundreds and thousands of years, sometimes taking a slightly new form or existing under a new name.
The first post will highlight the essential issue that drives the other issues and causes people to deny the preexistence of the Son before the virgin birth, and the presence of the other Persons of the Godhead. This issue has to do with a supposed conflict between Matthew 28:19 and Acts 2:38, the former commanding us to "baptize in the name of the Father, and of the Son, and of the Holy Spirit, while the later commands sinners to "be baptized in the name of the Lord Jesus Christ." It is this issue that, in the early 20th century, sparked the modern "oneness" heresy and opened the door for a complete denial of the trinity.