A special exercise of the Divine power upon the writers of the books of the Bible in virtue of which God Himself is the principal author of these books and man is the subordinate author. Though God used man as His instrument in writing these books, He did so in harmony with man's nature, no violence being done to the natural activity of his human faculties. The classical explanation of how God inspired the sacred writers is contained in Pope Leo XIII's Encyclical "Providentissimus Deus" (The God of all Providence):
"For by supernatural power God so moved and impelled them to write, He was so present to them, that the things which He ordered and those only they first rightly understood, then willed faithfully to write down, and finally expressed in apt words and with infallible truth."