Martin Luther's 95 Theses, published in 1517, were significant as they challenged the practices of the Catholic Church, particularly the sale of indulgences. Luther's criticisms sparked the Protestant Reformation, a religious movement that sought to reform Christianity and led to the creation of various Protestant denominations. His ideas emphasized personal faith, scripture's authority, and the priesthood of all believers, undermining the Catholic Church's power. The Theses encouraged widespread debate, questioning the established church authority, and ultimately led to profound changes in religious thought, social structure, and politics in Europe, fostering greater individualism and religious plurality.