Philosophy began by daring to explain nature without gods

Gottlieb identifies the pre-Socratic thinkers of Ionia as making a genuinely new move: proposing that natural events like storms, earthquakes, and the origin of the cosmos might have impersonal, discoverable causes, rather than being the direct will of gods reacting to human affairs. Thales' guess that everything derives from water, or Anaximander's more abstract 'boundless' source, were probably wrong in their specifics, but the method behind them was the real breakthrough.

What made this radical wasn't the accuracy of any particular answer but the underlying assumption: that nature operates according to consistent principles a person could reason toward, rather than remaining permanently mysterious or arbitrary. This assumption is the quiet foundation beneath essentially all later science and philosophy.

Gottlieb is careful not to overstate the pre-Socratics' sophistication — many of their specific claims were speculative guesses with little supporting evidence — but credits them with opening a door that has stayed open ever since. The first philosophers' real achievement was assuming nature was explainable at all.