***Then I would think him in error, as the Baptized person is of import not the Baptizer.***
Then why can one not just jump in a creek or swimming pool and declare himself self-baptized? Is it valid?
I can think of a false prophet who self-baptized himself before starting his cult.
Can a man and woman be self-married? Is it valid?
If a man and a woman said to each other the before God they were married, the state my not agree but I (and is my opinion) they would be as married as they could be.