Anaximander

Anaximander was a sixth-century BCE Greek philosopher who proposed the apeiron, an indefinite origin of all things, and produced an early map of the known world.

Apeiron: Anaximander’s indefinite, boundless origin from which all things emerge and to which they return. This is the foundational principle Anaximander proposed to explain the origin of the cosmos.
Pre-Socratic cosmology: Early Greek accounts of the universe that sought natural principles and processes behind its structure. Anaximander used natural processes to explain cosmic order without relying solely on divine genealogy.
Anaximander's map: An early Greek map of the inhabited world traditionally attributed to Anaximander. It exemplifies his effort to represent the known world systematically.
Theophrastus: An ancient Greek philosopher whose writings on earlier thinkers survive largely through later authors. Much of the testimony about Anaximander’s doctrines ultimately depends on Theophrastus.
Thales's water principle: Thales’s reported claim that water is the underlying principle of all things. Unlike Thales’s definite substance, Anaximander’s apeiron is indefinite.
Milesian school: A group of early Greek thinkers associated with Miletus who sought natural explanations for the cosmos. Anaximander belonged to this tradition of explaining nature through underlying principles.
Cosmic justice: Anaximander’s account of opposing things making reparations to one another over time. It frames the changing elements as constrained by an order that prevents any one from ruling forever.
Anaximander's treatise On Nature: A lost prose work on nature attributed to Anaximander, known through later quotations and reports. It is the source tradition for his cosmological ideas, though the work itself does not survive.
Aristotle: An ancient Greek philosopher whose works discuss earlier theories of nature and their first principles. His accounts shaped later interpretations of Anaximander’s apeiron and cosmology.
Anaximenes's air principle: Anaximenes’s claim that air is the underlying principle, changing through rarefaction and condensation. His definite material source contrasts with Anaximander’s boundless origin.

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