Writing systems are thousands of years old and are found in ancient Sumer, China, and Egypt. But even in the most literate ancient societies only a small fraction of people ever learned to read, rarely more than 10 percent. So, when did people decide that everyone should learn to read?

The move toward mass literacy began in the 16th century with the belief that every person should read and interpret the Bible for themselves. This belief began to rapidly diffuse across Europe with the eruption of the Protestant Reformation. It was initiated in 1517 by Martin Luther’s delivery of his famous 95 theses. Protestants came to believe that children had to study the Bible for themselves to better know their God. In the wake of the spread of Protestantism, the literacy rates in Britain, Sweden, and the Netherlands rose. Motivated by eternal salvation, parents and leaders made sure the children learned to read.

Religious beliefs also helped spur the beginning of state-funded schooling. As early as 1524, Martin Luther emphasized the need for parents to ensure their children’s literacy and placed the responsibility for creating schools on secular governments. In the 16th century, reformer John Knox pressured the Scottish government to initiate free public education for all children. One of his reasons was that everyone should have the skills to study the Bible.