That is the trouble with Jimmy Akin and the others like him. Who cares if it is “thoroughly Biblical”? These lay psuedo-theologians with blogs are so eager to please protestants they don’t “preach” from a Catholic viewpoint. It is not necessary to “prove” something is specifically Biblical to establish if it is true. The Catholic Church is not founded upon the Bible as a written historical document with some nice platitudes and good advice. It is founded upon the person of Christ himself.
As is any church The only foundation of any church is Christ And He gave us His written word to guide us. All that is needful to know for salvation is contained in the Scripture It is the final Authority until we are with Christ and see Him face to face