Heresies have been connected to Christianity from the beginning. Because this is a historical more than theological blog, I’m defining a heresy as a smaller group breaking off from the main group with significantly different doctrines.
Some time ago I taught a course on what are often called cults or sects. I was amazed at how many connections there were between these newer religious movements and heresies in the early church.
Gnosticism – Christian Science
Gnosticism is more of a movement than a group, as there are many types of Gnosticism. It was very much influenced by Platonic philosophy and the idea that matter is bad and spirit/mind is good. Gnostics taught there was secret knowledge (Greek: gnosis) that revealed that matter was an illusion and that we were really spirit. It it was incredibly influential in the early church.
In the 19th century, Mary Baker Eddy started a movement called Christian Science. Christian Science emphasizes healing but it is not the same kind of healing that we see in Pentecostal churches. Eddy taught that healing came from understanding that we are spirit and not body. We can be “healed” of cancer by understanding that not only does the cancer not exist, neither does our body.
Arianism – Jehovah’s Witnesses
Arianism is named after Arius, a church leader who spoke out against the Trinity. He taught that Jesus was different from the Father, specifically that Jesus was a created being. This was so influential that the famous Council of Nicaea was called to deal with the Arian question.
In the 19th century, Charles Taze Russell began the movement that would become the Jehovah’s Witnesses. They rejected the Trinity and believed that Jesus was not God but was a created being, specifically the Archangel Michael.
Modalism – Onenness Pentecostals
This is also called Modalistic Monarchianism. This early heresy also rejected the Trinity but in a different way than Arius. Modalists affirm the full deity of Jesus but focus more on the oneness of God. This means that the one God can at times manifest in different modes, whether the Father, the Son or Spirit, but without any plurality within the Godhead.
Oneness Pentecostals began in the early 20th century. It emerged out of reflection of the baptismal formulas: baptizing in the name of the Father, Son and Spirit, and baptizing in the name of Jesus. It was concluded that the name of the Father, Son and Spirit was Jesus. There was one God named Jesus, who was revealed in the Old Testament as the Father.
Ebionites – Unitarians
The Ebionites were early Jewish followers of Jesus. They accepted Jesus as the messiah but rejected the idea of the Trinity or the deity of Jesus.
When I talk of Unitarians, I mean the original form coming out of the Enlightenment and not the more recent version after their merger with the Universalists. The original Unitarians were successors of the Puritans and the Congregationalists. They accepted most Christian teachings but concluded that Jesus was a human messiah rather than God incarnate.
I have tried to figure out the ancient equivalent of the Latter-day Saints. I’m leaning toward Pelagianism, but I need to do more research.
The basic conclusion is that there is nothing new. Heresies now began as heresies then.
The Christian church has had an unfortunately bad relationship with the Jewish synagogue at various times in their history. But is Christianity antisemitic at it’s core? The earliest Christianity can be found in the documents of the New Testament.
One of the first books that I read was Kenneth Scott Latourette’s A History of Christianity Vol. 1. It helped to spark my interest in church history. I recently reread both volumes of this respected history.
Papias is the most important church father that you have never heard of. Even though none of his writings survive in anything beyond fragments in other writings, he is still influential and is often consulted by New Testament scholars for his traditions about the origins of the Gospels.
This post is not on whether or not Jesus was conceived by Mary while she was still a virgin. I deal with more theological questions at my other 
.