Born to a simple farming family in Scotland, John Knox would become known to history as the leader of the Scottish Protestant Reformation. He is also regarded as the founder of the Presbyterian sect of Christianity.

Despite his humble upbringing, Knox received an elementary education in Haddington. His mother died when he was a young boy, and while his father encouraged him to take up farming, that occupation had no appeal to Knox. He was not interested in becoming an apprentice, either. The only other option to someone of his station was to study for the priesthood. A number of men chose that path as a way to receive an academic education, even if they later decided against taking clerical orders. Later, he attended the University of St. Andrews, and was a student of one of the greatest scholars of the age, John Major.

Following college, he took a position as court notary, but within three years the record states that he was a "minister of the sacred altar in the diocese of St. Andrews, notary by apostolic authority." He also became a tutor to the sons of prominent Scotsmen, including those who were active in ideas of Reformation. Perhaps the greatest reformer to influence Knox was George Wishart, who had fled Scotland some years earlier to avoid punishment for heresy. Knox joined forces with Wishart once the latter returned to Scotland, and the two had a number of close calls with both parochial and civic officials. Knox somehow avoided arrest at that time.

Approximately one year later he delivered a powerful sermon, in which he outlined what would become key components of the Scottish Reformation. These ideas included the Bible as absolute authority, the doctrine of justification by faith alone, and the rejection of the mass, purgatory and prayers for the dead. That same year, prompted by Mary of Guise (Mary, Queen of Scots' mother, who was serving as her regent), the French stepped in to put a stop to Protestant activities and reforms. France sent galley ships to Scotland, where Knox and others were seized and held on board, chained and whipped for a period of nineteen months.

Once he was released, Knox fled to England, where Reformation was considered a much less radical idea. He began to preach in English churches. His reform ideas and tales from his treatment at the hands of the French drew in large crowds. While in England, he met the woman he would marry, Marjorie Bowes. She came from a well-placed, old and wealthy family, who did not approve of the match. Life in England was good to Knox, but when the young Protestant King Edward VI died, his Catholic half-sister came to the throne, and Knox left the country, traveling to the European continent. From Zurich, Switzerland he wrote pamphlets that were published and sent to England, denouncing the Catholic Queen Mary and her burnings and executions of Protestants.

Later, when Mary Stuart came to majority, she assumed the full role of Queen of Scotland. Knox came to Scotland and publicly rebuked her. She listened to what he had to say, but then asked him to work to encourage religious tolerance. During their third conversation, Mary turned to tears in an attempt to secure Knox's cooperation. He responded  by saying, "Madam, in God's presence I speak: I never delighted in the weeping of any of God's creatures; yea I can scarcely well abide the tears of my own boys whom my own hand corrects, much less can I rejoice in your Majesty's weeping."

However, he continued, he would rather endure her sobbing than "betray my Commonwealth" with silence. Mary immediately ended the interview. Knox married a second time, to a distant relative of Queen Mary of Scotland. Her name was Margaret Stewart and the union was considered quite controversial. The couple had three daughters. Despite the violent times in which he lived, and the fact that he often invited danger into his life, Knox lived into old age, continuing to preach, often critiquing Mary and even calling for her death. In his will, Knox stated that "None have I corrupted, none have I defrauded; merchandise have I not made."