The Bible

John Calvin said that we ought “to attempt nothing but by Divine authority.” Next question -- Where is that Divine authority found?
-Not the church
-Not within yourself
-Not culture
-Not government
-Not your personal experience
-Not some new revelation
-Not some priest, nor pope

Divine authority is found in the 66 books of the Bible. (sorry, no Apocrypha) Every word is inspired of God and every word is infallible. Therefore, the Bible alone is the final authority. So, yes, "Scripture Alone" should be the motto of every believer. We test all things by Scripture -- all doctrines, all churches, all our actions, all councils, preachers, priests and popes.

If you are not reading the Bible, learning the Bible and following the Bible, you are living for yourself and have put yourself or something else in the place of authority. If you don't know Scripture, you can't live by Scripture, and if you don't live by Scripture, you are not living by the authority of God. It is in Scripture that we learn about Christ, who is the only way of salvation. It is in the Bible that we find out that "by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast." ~ Ephesians 2:8,9

Divine authority is found in Scripture, which is God's holy, inspired, inerrant, infallible Word.

"All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness, that the man of God may be complete, thoroughly equipped for every good work." ~ 2 Timothy 3:16-17

"To the law and to the testimony! If they do not speak according to this word, it is because there is no light in them." ~ Isaiah 8:20

"The entirety of Your word is truth, and every one of Your righteous judgments endures forever." ~ Psalms 119:160

"Forever, O LORD, Your word is settled in heaven." ~ Psalms 119:89

"These were more fair–minded than those in Thessalonica, in that they received the word with all readiness, and searched the Scriptures daily to find out whether these things were so." ~ Acts 17:11

The Authority and Inspiration of the Scriptures - B. B. Warfield
http://homepage.mac.com/shanerosenthal/reformationink/bbwauthority.htm