The Holy Spirit was not included in the Council of Nicea, does this mean He is not God?
I agree with you that the Holy Spirit issue was not included in the Council of Nicea. How can you debate an argument or a heresy before its existence? When the bishops met at Nicea; no one at that time had doubted the person of the Holy Spirit as one with the Father and the Son and proceeding from the Father. Normally, it is only when a controversial issue or a heresy arises, that an Ecumenical council is convened to investigate the matter at hand in order to come up with a canon concerning it. The divinity of the Holy Spirit was discussed in the Council of Constantinople.