The following is summarized from Arnold Snyder, “Word and power in Reformation Zurich”, Archiv für Reformationsgeschichte, vol. 81 (1990), pp263-285:
“It was during this early stage of struggle against the traditional church (in which the question of ecclesiastical authority was paramount) that Zwingli expressed most fully his views concerning the overriding authority of Scripture and the right of all believers to read and interpret Scripture. In August 1522, following the public breaking of the Lenten fast, a confrontation with the bishop’s representatives, and an admonition from the bishop of Constance, Zwingli published the Archeteles in which he devoted an important section to the question of Bible reading and interpretation by the laity. ‘I want to leave you here for reflection from time to time the shameless statement of a certain smatterer who ventured to proclaim in a public assembly that it was unlawful for laymen to know or to read the gospel, but only for those to whom that function had been entrusted; namely, for our little priests and masters…. Country bumpkins! Do you not see that the spirit of God is everywhere like unto itself and ever the same? The more unskilled a man is in human devices and at the same time devoted to the divine, the more clearly that spirit informs him, as is shown by the apostles and by the foolish things of this world which God has chosen …. It is not the function of one or two to expound passages of Scripture, but of all who believe in Christ (Non unius esse videtis aut alterius de scripturae locis pronunciare, sed omnium qui christo credunt).’ At this early date Zwingli appeared sanguine indeed about the possibility of simple, lay people expounding Scripture, a position he would later come to regret.
Zwingli developed his ideas further in Of the Clarity and Certainty of the Word of God, published less than a month after the Archeteles. Zwingli argued that the Word of God is all-powerful, perspicuous and sufficient of itself to lead the truth. All human beings have an innate spiritual capacity that can recognize the truth of God’s Word, when the Spirit of God is allowed to lead. The Word of God brings its own certainty, with no need of human intervention. What is needed, quite simple, is a humble spirit, God’s grace, and a willingness to be led to truth by God’s Word. Human wisdom, philosophy and man-made ceremonies only divert believers from the truth; in fact, the simple are more disposed to receive God’s truth than are the ‘wise’ (Matt. 11:25).”
This extended quote from Snyder reminds us of Zwingli’s role in stressing the perspicuity of Scripture. Zwingli, of course, was later to struggle against the Anabaptists and their interpretation of Scripture.