Guido da Castello was an Italian philosopher and theologian active in the late 13th century. He is best known for his contributions to the study of scholasticism, a method of critical thought that dominated medieval universities. His works often focused on the relationship between faith and reason, exploring how they could coexist in understanding the divine. He is also recognized for his influence on the University of Paris, where many of his ideas were discussed and debated. Guido's writings contributed to the development of medieval philosophy, particularly in the areas of metaphysics and ethics, shaping the intellectual landscape of his time.