This two part course from the University of Pennsylvania (Part 1 here – Part 2 here) “traces the origins of philosophy in the Western tradition in the thinkers of Ancient Greece,” beginning with “the Presocratic natural philosophers who were active in Ionia in the 6th century BCE and are also credited with being the first scientists.” The course description continues:
Thales, Anaximander, and Anaximines made bold proposals about the ultimate constituents of reality, while Heraclitus insisted that there is an underlying order to the changing world. Parmenides of Elea formulated a powerful objection to all these proposals, while later Greek theorists (such as Anaxagoras and the atomist Democritus) attempted to answer that objection. In fifth-century Athens, Socrates insisted on the importance of the fundamental ethical question—“How shall I live?”—and his pupil, Plato, and Plato’s pupil, Aristotle, developed elaborate philosophical systems to explain the nature of reality, knowledge, and human happiness. After the death of Aristotle, in the Hellenistic period, Epicureans and Stoics developed and transformed that earlier tradition.
You can take these courses for free by selecting the audit option upon enrolling. If you want to take the courses for a certificate, you will need to pay a fee.