From Citizendium - Reading time: 2 min
Pre-Socratics refers to the early Greek philosophers who generally lived before Socrates and were not influenced by him.
Aristotle was the first who noticed that with Socrates philosophy had taken a new turn. With Socrates' emphasis on humanism and ethical values he distinguished himself from prior philosophers like Thales and Anaximander who in the first place had stressed natural philosophy and cosmology.
Unfortunately all they have left us are fragments of writing in the form of reports and criticisms of later writers who commented on them and the reconstructions of their philosophy by scholars leaves us with incomplete understanding of the views they held. One our best secondary sources is Aristotle who at the time seemed to have had access to their writings. But even his interpretation is biased by his own views on philosophy. It basically remains a controversial field of study. Another important source is Theophrastus, considered to be the first professional historian of philosophy who discussed pre-Socratic writings systematically.
Thales (624-546 BCE) - Anaximander (610-546 BCE) - Anaximenes (585-525 BCE) -
Pythagoras of Samos (582-496 BCE) - Philolaus (470-380 BCE) - Alcmaeon of Croton - Archytas (428-347 BCE).
Heraclitus of Ephesus (535-475 BCE)
Xenophanes of Colophon (570-470 BCE) - Parmenides of Elea (510-440 BCE) - Zeno of Elea (490-430 BCE) - Melissus of Samos (born c. 470 BCE)
Empedocles of Agrigentum (490-430 BCE) - Anaxagoras of Clazomenae (500-428 BCE)
Leucippus (5th century BCE) - Democritus of Abdera (460-370 BCE)
Diogenes of Apollonia (born c. 460 BCE)
Protagoras (490-420 BCE) - Gorgias (487-376 BCE) - Hippias (485-415 BCE) - Prodicus (465-390 BCE)