Anaximenes was a philosopher who lived in the 6th century BC in the city of Miletus, which was located in the region of Ionia in ancient Greece. He was one of the Milesian philosophers, a group of early philosophers who were associated with the city of Miletus and who are credited with laying the foundations of Western philosophy. Anaximenes is known for his contributions to the development of the philosophical concepts of matter and causation, and for his belief in a single, divine substance that underlies all reality.