Desiderius, often referred to as Desiderius Erasmus, was a Dutch philosopher and theologian born in the late 15th century. He is best known for his works on humanism and his critical approach to the Catholic Church. Erasmus emphasized the importance of education and the study of classical texts, advocating for a return to the original sources of Christianity. His most famous work, In Praise of Folly, satirizes the corrupt practices of the church and society. Erasmus's ideas laid the groundwork for the Reformation and influenced many thinkers, including Martin Luther. His emphasis on reason and ethics continues to resonate in modern discussions of faith and morality.