passions of fallen man their natural powers even after the Fall, without "supernatural gifts". While in his pre-Pelagian writings Augustine taught that Adam's guilt as transmitted to his descendants much enfeebles, though does not destroy, the freedom of their will, Protestant reformers Martin Luther and John Calvin affirmed that Original Sin completely destroyed liberty (see total depravity). According to Leo Ruickbie, Augustine's arguments against magic, differentiating it from miracle, were crucial in the early Church's fight against paganism and became a central thesis in the later denunciation of witches and witchcraft. According to Professor Deepak Lal, Augustine's vision of the heavenly city has influenced the secular projects and traditions of the Enlightenment, Marxism, Freudianism and eco-fundamentalism. Post-Marxist philosophers Antonio Negri and Michael Hardt rely heavily on Augustine's thought, particularly The City of God, in their book of political philosophy Empire. Augustine has influenced many modern-day theologians and authors such as John Piper. Hannah Arendt, an influential 20th-century political theorist, wrote her doctoral dissertation in philosophy on Augustine, and continued to rely on his thought throughout her career. Ludwig Wittgenstein extensively quotes Augustine in Philosophical Investigations for his approach to language, both admiringly, and as a sparring partner to develop his own ideas, including an extensive opening passage from the Confessions. Contemporary linguists have argued that Augustine has significantly influenced the thought of Ferdinand de Saussure, who did not 'invent' the modern discipline of semiotics, but rather built upon Aristotelian and Neoplatonic knowledge from the Middle Ages, via an Augustinian connection: "as for the constitution of Saussurian semiotic theory, the importance of the Augustinian thought contribution (correlated to the Stoic one) has also been recognized. Saussure did not do anything but reform an ancient theory in Europe, according to the modern conceptual exigencies." In his autobiographical book Milestones, Pope Benedict XVI claims Augustine as one of the deepest influences in his thought. Oratorio, music Marc-Antoine Charpentier, Motet "Pour St Augustin mourant", H.419, for 2 voices and contino (1687), and "Pour St Augustin", H.307, for 2 voices and continuo (1670s). Much of Augustine's conversion is dramatized in the oratorio La conversione di Sant'Agostino (1750) composed by Johann Adolph Hasse. The libretto for this oratorio, written by Duchess Maria Antonia of Bavaria, draws upon the influence of Metastasio (the finished libretto having been edited by him) and is based on an earlier five-act play Idea perfectae conversionis dive Augustinus written by the Jesuit