I'm as flummoxed by soycd as you are, but I'm afraid the above statement is wrong.
Only G-d Himself is self-authenticating. The Bible can only be believed because G-d has vouched for it.
It’s self-authenticating in that the Lord authenticates it to those whom He is saving. Only He can give us understanding. John 6:45 teaches that all those being saved are “taught of God.”