Oneness believers commonly treat the Father and the Holy Spirit as exactly the same: the deity side of Christ. This video proves why They can't possibly be the same person.

Moreover, if Modalism is correct, John 16:13-15 would lead to the strange idea that the Father has to submit to the authority of His Son and hear and take things from the Son to disclose. That's impossible.

I'm interested in knowing the Oneness response. Haven't heard one yet.

Proving the Holy Spirit is not the Father leads to the collapse of Oneness theology.