“Modalism” is the idea that we can explain the relationship of God, Jesus, and Holy Spirit by saying there is only one God, and three expressions or forms God has taken.
It’s a fantastic idea! It would be identical to saying H2O takes the form of vapor, liquid, solid. That makes perfect sense.
It’s just too bad this “Sabellianism” is heresy. Ask Servetus, who was invited to a barbeque by Calvin. Ask T.D. Jakes, who was once billed as the next Billy Graham, gracing the cover of Time magazine, until …
There is then no explaining in any coherent way how God is “One In Three, yet Three persons”. It is utter gibberish. It is literal gibberish. The idea can have no import to Christianity in the least! Why? It is incoherent. It cannot be explained nor can it then be used to explain anything else.
If God has properties x, y, and z and God, Jesus, and Holy Spirit are all “fully God”, then Jesus and the Holy Spirit also have properties x, y, and z. But to say God, Jesus, and the Holy Spirit are three distinct persons is to say they also have different properties. For convenience:
G(x, y, z)
J(x, y, z, l, m, n)
S(x, y, z, o, p, q)
This shows G (God), J (Jesus), S (Holy Spirit) in fact can be said to be “fully God”. It also, by definition, illustrates the impossibility of “Hypostasis”, given any distinction makes “co-substantiality” incoherent when forcing these claims together.
A mother, a father, their child form a family. But if this is fitting, neither mother, father, nor their child can be “fully family”. And neither mother nor father nor child are “family” at all without the others. So, each are essential to “family”, none are family alone, and hence, it is the different properties of each that “family” is contingent on. In other words, x, y, and z are necessary for “family”, but without l, m, n, o, p, q, there is no “family”. We can put it this way:
Family(x, y, z)
Either Modalism makes sense, or “Tritheism” makes sense, but there’s no rationally coherent means of claiming both are true of the Trinity and both are false of the Trinity at the same time.
Jefferson astutely notes, the Trinity is the Abracadabra of mountebanks calling themselves the priests of Jesus.