Pierre Hadot's formulation of “spiritual exercise” has had a tremendous influence upon the study of philosophy and religion in Late Antiquity and beyond. He argues that the well-known exercises of Ignatius of Loyola are part of an older and broader tradition that has its roots in Greco-Roman and Hellenistic schools of philosophy, and that much of ancient and late ancient philosophical speculation should be analyzed as deeply intertwined with practical goals for self-transformation. His research centers upon the Greek askēsis and meletē, which he translates as “spiritual exercise,” as well as the Latin exercitium spirituale. However, his study goes beyond occurrences of those particular terms, and he aims to develop a category that can be used in comparative and theoretical reflection.Hadot's studies of spiritual exercises run through his works, including Plotinus, or the Simplicity of Vision. Michael Chase, trans. (Chicago: University of Chicago Press, 1993); Philosophy as a Way of Life Arnold Davidson, ed., Michael Chase, trans. (Cambridge, MA: Basil Blackwell, 1995), esp. pp. 81–144; and The Inner Citadel, Michael Chase, trans. (Cambridge, MA: Harvard University Press, 1998). An important predecessor is Paul Rabbow, Seelenführung: Methodik der Exerzitien in der Antike (Munich: Kösel-Verlag, 1954).