I disagree with the point made around the 50 minute mark that some scholar said that a Quaternity is just as feasible as the Trinity if one bases one's arguments on after-the-fact reasons. But I disagree. God the Son enters his creation so that is the 2nd Person. God the Father is not seen. And God the Spirit indwells people who are born-again. It wouldn't make sense for there to be two Sons since one Son is enough. Should I say to myself the two Christs live in me by the Holy Spirit? That makes no sense. It wouldn't make sense for me to have two spirits for one Holy Spirit is enough. And there can only be one Father above of the Son. Where have you ever heard of a Son having two Fathers? If you say there are two Fathers then why would that be so, and which of these two Sons belongs to which of the two Fathers? Do you see adding unnecessary confusion is unnecessary?