I am not sure Sharp's rule is much of a rule at all. Most trinitarian exegesis begins witht he premise that the Trinity is true and works from there. JW's guilty of the same thing. I went through a phase when i thought there might be something to it. The basic trinitarian non-heretical doctrine has evolved around this consideration of "nature". Something along the lines of we all here on this board share a nature that is human. So while we are separate people, we are all human.
I get it, but it isn't in my humble opinion analgous. As long as God knows something that his son does not, there is no Christian Trinity.
Wether it is neccesary to believe that in order to be accepted by God, only people on both sides of the issue have beef with it. I personally think that considering scripture, exactly what was expected for us to have understood is exactly what was said. The explanation was condecended down to terms we could understand. Father and son. I understand exactly what that is.
If you want more info on Sharps, I think that Stafford third book has more on it.
Anyone know what happened to that guy? Where he is now? His site is basically dead.