Written on Stone vs. Written in a Book
This argument would be valid except for the fact that the 10 commandments were actually written twice by Moses in the book of the law. Since the Ten Commandments were also written by the hand of Moses in both Exodus 20 and Deuteronomy 5. It is more accurate to say that both were written in the book but only the 10 commandments were written in stone.
They were written by the hand of Moses in a book BEFORE they were written by the finger of God (Exodus 24:7; 31:18). Although the original 10 commandment law was written by the finger of God on stone, Moses recorded the 10 commandments twice with his own hand in the book.