Simply stated, the Protestant doctrine of sola Scriptura (“Scripture alone”) teaches that every teaching in Christian theology (everything pertaining to “faith and practice”) must be able to be derived from Scripture alone. This is expressed by the Reformation slogan Quod non est biblicum, non est theologicum (“What is not biblical is not theological,” cf. Dictionary of Latin and Greek Theological Terms: Drawn Principally from Protestant Scholastic Theology, Richard A. Muller, Baker, 1985).
An essential part of this doctrine, as it has been historically articulated by Protestants, is that theology must be done without allowing Tradition or a Magisterium (teaching authority) any binding authority. If Tradition or a Magisterium could bind the conscience of the believer as to what he was to believe then the believer would not be looking to Scripture alone as his authority.
A necessary corollary of the doctrine of sola Scriptura is, therefore, the idea of an absolute right of private judgment in the interpretation of the Scriptures. Each individual has the final prerogative to decide for himself what the correct interpretation of a given passage of Scripture means, irrespective of what anyone-or everyone-else says. If anyone or even everyone else together could tell the believer what to believe, Scripture would not be his sole authority; something else would have binding authority. Thus, according to sola Scriptura, any role Tradition, a Magisterium, Bible commentaries, or anything else may play in theology is simply to suggest interpretations and evidence to the believer as he makes his decision. Each individual Christian is thus put in the position of being his own theologian. …..