2 Timothy 3:10-17 (ESV)

10 You, however, have followed my teaching, my conduct, my aim in life, my faith, my patience, my love, my steadfastness, 11 my persecutions and sufferings that happened to me at Antioch, at Iconium, and at Lystra—which persecutions I endured; yet from them all the Lord rescued me. 12 Indeed, all who desire to live a godly life in Christ Jesus will be persecuted, 13 while evil people and impostors will go on from bad to worse, deceiving and being deceived. 14 But as for you, continue in what you have learned and have firmly believed, knowing from whom you learned it 15 and how from childhood you have been acquainted with the sacred writings, which are able to make you wise for salvation through faith in Christ Jesus. 16 All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, 17 that the man of God may be complete, equipped for every good work.

What is Scripture?  What is its nature and authority?

The Roman Catholic Church taught that Church tradition and the Scriptures are dual sources of ultimate authority for what men are to believe concerning God and how they might glorify Him.  The Reformed Churches teach, with the Scriptures, that the Word of God alone is breathed out by God and profitable to present men holy and complete before God.