Historical modernity and modern philosophy are not in sync. The former begins at that great confluence of inventions, conquests, and discoveries that characterize the second half of the 15th century, most importantly, Gutenberg’s press, the fall of Constantinople, and the discovery of America; the latter begins only in the 17th century with Bacon, Hobbes and Descartes. The Renaissance humanism of the 15th and 16th centuries, as well as the Protestant Reformation can be regarded only as a transitional period leading to modern philosophy proper in the 17th and 18th centuries. After Kant dies (1804), we can say that reason has failed, and that the foundations of the irrationality so pervasive today begin. It is that period of growing irrationality from Kant to after the Great Wars that we will call here contemporary philosophy; the period after that, you can give it the name you want.
Thales gave rise to philosophy by relying on sensory experience and reason. The next philosopher in line — Heraclitus — not only trailed a different path, but ignited a chain-reaction that ran through history toppling like dominos all that man tried to erect with his reason. It all began with the problem of change and multiplicity; it all ended with my thirteen-year-old niece asking petulantly: “Why can’t I simply decide I am a boy?”