The Bible mentions God the Father, God the Son, and the Holy Spirit, and yet Christian believe that there is only one God. This idea, called Trinity, was started at the First Council of Nicaea, in 325, and developed during several church meetings or councils. Today, many Christian groups agree with it. Oriental Orthodox Churches did not agree with the idea, and split after the council. The biggest of the Oriental Orthodox is the Coptic Orthodox Church. The Oriental Orthodox Churches agree with the ideas in the First Council of Nicaea, but they disagree with other councils.