Socrates (469-399 BCE) is, next to Plato and Aristotle, considered the greatest philosopher of antiquity. He was such an important figure that periods in the history of philosophy can be divided into pre-Socratic and post-Socratic.
The Socratic Method, ascribed to him, is a way of conducting dialogue and at the same time reaching the truth. Its principles are still valid today and you can quickly notice a connection with modern coaching. I wrote about it, among others in a dedicated post Did coaching come before Christ?
Socrates was a thinker who was not interested in postulating truths, but in examining the very foundations of thought. He did not take anything for granted, and that is what makes his famous statement:
"I know that I know nothing."