"For those who while pretending to cite the faith confessed at Nicaea, venture to blaspheme the Holy Spirit, deny Arianism in words only, while in thought they return to it." - Church in ANtioch
Macedonianism (Also called Pneumomatomachianism or Tropicianism) is the belief that the Holy Spirit is not an eternal member of the Godhead, but instead a being or force created by God the Father.
Macedonianism is very similar to Arianism, which claims that Jesus is a creation of God rather than an eternal member of the Godhead. In fact, many Macedonians are also Arians and vice versa.
Why is it Heresy?
Macedonianism is heresy because it denies the divinity of the Holy Spirit and the doctrine of the Trinity. By doing these two things, Macedonianism is setting up an idol and worshipping a false god.
Macedonianism is named after its founder, Macedonius of Constantinople.
Macedonianism was first taught by Macedonius in the 360s, near the end of his life. Most of the followers of Macedonius rejected Arianism, but also rejected the orthodox view that was proclaimed at Nicea. Many of the Macedonians decieved believers by merely claiming "We believe in the Holy Ghost," similar how to a Catholic may say, "We don't worship Mary," or how a Mormon may say, "We believe in Jesus." Serapion of Thumis noticed the growth of this heresy within Alexandria and told his friend, a popular teacher named Athanasius, about this. This lead to Macedonianism being condemned at the Council of Alexandria in 362 AD, which was lead by Athanasius and Eusebius. The Church in Antioch sent a letter out condemning, "those who say that the Holy Spirit is a creature and separate from the essence of Christ." It continued, "For those who while pretending to cite the faith confessed at Nicaea, venture to blaspheme the Holy Spirit, deny Arianism in words only, while in thought they return to it." Despite this, the heresy grew. Another council was held in Antioch in 363, also condemning Macedonianism. Throughout the 370s, the Eastern Church started to heavily condemn Macedonianism. Amphilochius of Iconium, Basil of Caesarea, and Gregory of Nyssa all pushed for the elimination of this heresy. By the 400s, the heresy had started to die off.
In the 1700s, the Socians taught both Arianism and Macedonianism. They claimed that both Jesus and the Holy Spirit were merely creations of the Father. During the same century, the Moravians, a dangerous Theoerosist sect, taught that the Holy Spirit was born in the wound at Jesus's side where he was stabbed with a spear.
In modern times, this heresy is still promoted by the Jehovah's Witnesses.