With the advent of the Christian era and the eventual outlawing, in 529 C.E., of the ancient philosophical schools (by Roman Emperor Justinian), philosophy conceived of as a way of life largely disappeared from the West. Its spiritual practices were integrated into, and adapted by, forms of Christian monasticism.The philosophers’ dialectical techniques and metaphysical views were integrated into, and subordinated, first to revealed theology and then, later, to the modern natural sciences.
However, the conception of philosophy as a way of life has never completely disappeared from the West, resurfacing in Montaigne, Rousseau, Goethe, Thoreau, Nietzsche, and Schopenhauer, and even in the works of Descartes, Spinoza, Kant, and Heidegger.
What is Ancient Philosophy?
Background on Pierre Hadot