Joseph Calasantius, Spanish priest and saint, friend of Galileo, is the brilliant pioneer of popular free schools in Europe. An eternal innovator, he is one of the great educators of all times. He founded the Order of Poor Regular Clerks of the Mother of God of the Pious Schools (Escolapios), now found all over the world. For his ideal, he was persecuted and betrayed. Denounced before the Inquisition, he was removed from his position and saw his work destroyed. It would only be restored after his death. Admired as a precursor of modern teaching, he was able to make reality the motto he inculcated in thousands of disciples: “piety and knowledge”.