Catholics always ask, "Where do you find Scripture alone as the supreme authority for faith in the Bible?" The answer should be obvious since there is no higher authority than almighty God and He has exalted His Word above all things and equal to His holy name (Psalm 138:2). The Bible's supreme authority is established by its divine origin. It is the most authoritative, influential and powerful book ever written. God chose forty men to pen His word as they were carried along by the Holy Spirit (2 Peter 1:21).
The writers claimed they were transmitting the very word of God, infallible and authoritative to the highest degree. God's word is sufficient to function as the sole, infallible rule of faith because the Bible does not refer to any higher rule of faith. Everything that we must know, understand and believe to become a Christian is found in the Scriptures (1 Cor. 15:1-4).
The Apostle Paul wrote: "from infancy you have known the Holy Scriptures, which are able to make you wise for salvation through faith in Christ Jesus" (2 Tim. 3:15-16). All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, (2 Tim. 3:15-16).
The Apostle Paul commended the Bereans for using Scriptures to verify the truthfulness of his teaching. Since an apostle, who penned over half the New Testament was tested by the Bible, all religious teachers must be tested using the same Scriptural authority. The Bereans... received the message with great eagerness and examined the Scriptures every day to see if what Paul said was true (Acts 17:11). After considering all other sources of authority we must always ask, "But what does the Scripture say?" (Galatians 4:30). Since it is impossible for God to lie, His word must be the standard by which we discern truth from error (Hebrews 6:18; 1 John 4:6). The Lord Jesus used the power and authority of the Scriptures to rebuke Satan (Matthew 4). "The word of God is living and active. Sharper than any double-edged sword, it penetrates even to dividing soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart (Hebrews 4:12). Those who reject the supreme authority of Scripture are easily deceived.