Born in Miletus, a wealthy port of Ionia tied to trade routes across the Aegean and Near East. The city’s merchants and sailors brought stories, measurements, and sky-lore that later fed his natural philosophy.

As a youth, he absorbed Milesian habits of explaining nature without myth, associated with the circle of Thales. Practical geometry from surveying and navigation likely influenced his later interest in measuring earth and sky.

Milesian intellectual life was energized by accounts linking Thales to the solar eclipse associated with the battle of the Medes and Lydians. In that atmosphere, he pursued broader explanations that went beyond a single material element.

He argued that the first principle is the apeiron, an indefinite and boundless source rather than water, air, or fire. This abstract move allowed opposites like hot and cold to emerge and contend within a wider cosmic order.

Ancient authors report that he wrote one of the first philosophical works in Greek prose, later known as 'On Nature.' Though the book is lost, a surviving fragment preserves his language of cosmic justice and balance.

He described a structured cosmos in which celestial bodies are arranged in rings or wheels of fire seen through openings. The scheme aimed to explain eclipses and regular motions through geometry rather than divine stories.

He claimed the Earth remains at rest because it is equally related to everything around it, needing no physical support. This symmetry-based reasoning challenged older images of a world held up by Titans or columns.

Later writers credit him with drawing a map showing seas and lands of the oikoumene, useful for travelers and civic planning. Building on Milesian seafaring knowledge, the map helped frame geography as a measurable science.

He offered natural accounts of winds, rain, and storms, treating weather as physical processes rather than capricious gods. Ancient testimonies also link him to ideas about seas drying and land emerging over long periods.

He proposed that living creatures first formed in wet environments warmed by the sun, then diversified as conditions changed. This naturalistic approach treated life’s origins as part of the same lawful cosmos as stars and weather.

He reasoned that human infants are too helpless to have survived in the earliest world without protection, implying an origin within other creatures. The claim stands as one of the earliest recorded evolutionary-style arguments in Greek thought.

In a commercial polis like Miletus, calendars, seasonal markers, and practical measurement mattered for agriculture and navigation. His work reflects that milieu, combining observation with bold hypotheses about scale and order in nature.

Ancient tradition places Anaximenes after him in Miletus, continuing the search for an arche with a more concrete element. Even where they disagreed, his example legitimized systematic argument over poetic authority.

His ideas circulated among Ionian cities linked by colonization and trade, where thinkers compared cosmologies and measurements. Later compilers such as Theophrastus and Simplicius preserved reports that kept his fragment alive.

During his later years, the balance of power in Asia Minor shifted as Cyrus the Great’s Persians expanded westward. In that uncertain climate, Milesian intellectual life still pursued inquiry into nature and the structure of the world.

He died around the time Lydia fell after Croesus’s defeat, an event that reshaped Ionian politics and trade. His name endured because later philosophers treated his apeiron and cosmology as a decisive step beyond mythic origins.