Scripture-first response
“A mediator must be a separate divine person.”
Paul identifies the mediator precisely as ‘the man Christ Jesus.’ His real humanity qualifies Him to represent us before the one God.
What the objection is claiming
The mediator’s distinction is located in a second divine identity instead of His genuine humanity.
1 Timothy 2:5
For there is one God, and one mediator between God and men, the man Christ Jesus;Open full referenceThe mediator is specifically the man Christ Jesus, representing humanity before the one God.
How the passages answer it
The incarnation supplies a true human representative who obeys, suffers, dies, rises, and intercedes. The fullness of God in Him makes His saving work God’s own action, while His humanity makes Him our brother and high priest.