Schmitt traces uses and development of the term from Marsilio Ficino (1433-99) and Giovanni Pico della Mirandola (1463-94) to Agostino Steuco (1497-1548), and finally to Gottfried Wilhelm Leibniz (1646-1716), passing along the way Symphorien Champier (c. 1472-c. 1539), Francesco Giorgio (1460-1540), Nicholas of Cusa (1401-64), and Guillaume Postel (1510-81). Among the moderns, he mentions briefly Jacques Maritain, Erwin J. Auweiler, Paolo Rotta, Aldous Huxley, Roberto Ardigo, Cornelius Kruse, Otto Willmann, Maurice de Wulf, and S. Radhakrishnan.
On Leibniz, he concludes:
Although it is more fashionable today to see Leibniz as a "precursor of modern logic and mathematics" or as a brilliant metaphysician, his affinity to the tradition of perennial philosophy as envisioned by Steuco is most clear. Leibniz's whole philosophy of harmony is very similar to that expressed by Steuco and the others we have discussed, although in Leibniz the metaphysical foundations of such a Harmonistik are much more carefully worked out, recalling in some ways Cusanus' attempt to give a metaphysical basis to a "philosophy of concord" . . . In a sense, Leibniz is the most eminent defender of the tradition called by Steuco philosophia perennis. Moreover, Leibniz's attempts to bring about religious unity-in a century not reputed for its ecumenical spirit-hark back to Cusanus, as well as to Ficino and Pico.For more on Leibniz and the perennial philosophy, see
- H. J. De Vleeschauwer, “Perennis quaedam Philosophia,” Studia Leibnitiana supplementa I (1968), pp. 102-22.
- R Meyer, “Leibniz und die Philosophia perennis,“ in Tradition und Kritik, Festschrift für Rudolf Zocher zum 80. Geburtstag (Stuttgart: Frommann-Holzboog, 1967) pp. 223-54.
My thanks to Anders Klostergaard Petersen for bringing the Leibniz connection to my attention in the first place.