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Wellsprings
cosmology

The First Principle

ἀρχή

The single 'first thing' — the ultimate source, principle, and stuff of the whole world, and the question that launched Greek philosophy.

The archē was the fundamental substance or source from which all things in the universe originate and to which they ultimately return. Early Greek philosophers, especially the Milesians like Thales, Anaximander, and Anaximenes, sought to identify this single underlying principle. Rather than explaining the world through myths or gods, they proposed that everything derives from one primary material—water, the infinite, or air—which persists through all changes and transformations.

This search for a first principle represented a revolutionary shift toward rational inquiry. When Thales claimed water was the archē, or when Anaximenes argued air held this primacy, they were making testable claims about nature itself, not appealing to supernatural causes. By identifying a single originating substance that endures beneath surface appearances, these thinkers created the foundation for Western philosophy and science, establishing that the natural world operates according to intelligible principles rather than arbitrary forces.

Where this idea shows up

58 Greek sources·1 Jewish-canon citation

Where to read it