The modalistic view of the Trinity found its clearest expression in the teachings of Sabellius in the first half of the third century. Sabellianism was rejected by the ecumenical councils of Nicaea, Constantinople, Ephesus, and Chalcedon.
According to the modalistic view, the one true God does not exist as three distinct, transcendent, immanent, infinite, eternal, and immutable persons: God the Father, God the Son and God the Holy Spirit. Instead, there is only one person in the Godhead who appears at different times in one of three different modes: God the Father, God the Son or God the Holy Spirit. Remnants of this view can be found today in the Oneness Pentecostalism movement.
The modalistic view does not explain the prayers of Jesus and His speaking objectively of the Father and of the Holy Spirit. This view also does not explain the actions of God the Holy Spirit and God the Father during the baptism of Jesus (Mat 3:16-17).
Finally, modalism cannot explain how each man and woman is capable of agape (unconditional) love for others. If each person is created in the image of God then agape love must one of God's attributes. But how can agape love be an attribute of God when, before the creation of heaven and the universe, nothing existed except God? Who would have been the object of God's agape love? The answer is simple for Christians. Each of the distinct, transcendent, immanent, infinite, eternal and immutable persons comprising the triune God (Father, Son and Holy Spirit) has always loved the other two unconditionally. This quandary becomes unresolvable only for those who believe God exists as one person. The "agape love" dilemma besets non-Christian religions (e.g. Islam) as well as Christian spinoffs (Oneness Pentecostalism).