The idea that there is ""one principle of all things, of which there has always been one and the same knowledge among all peoples." was first stated by Agostino Steuco (1497-1548) in his book "De perennia philosophia" (1540), building on the work of such neo-Platonist theologians as Marcilio Ficino and Giovanni Pico della Mirandola.

Steuco was attempting to show that certain basic truths were held in common between Christianity and classical philosophy. Later commentators added Eastern beliefs and practices to the mix, creating what is called 'Traditionalism'.

The Germ Theory of Disease developed in the 19th Century, but germs had been around long before. The ideas of the Perennial Philosophy were around for a long time before anybody built a coherent body of thought and teaching around them. Prior to that they were simply dogma in various faiths or axioms in various philosophies.