archí

Arché is a Greek term meaning beginning, origin, source, or first principle. In philosophy, it denotes the originating principle or ultimate cause from which things derive. The word has been used to describe both a concrete substance posited as the basis of the world and a more abstract organizing principle underlying change and existence.

In early Greek thought, various philosophers proposed different archai as the fundamental principle of all things. Thales is traditionally said to have identified water as archē; Anaximander posited the apeiron, the indefinite or boundless principle; Anaximenes argued for air as archē. Other thinkers, such as Heraclitus, emphasized fire or the process of becoming as a governing principle, while Parmenides argued that Being itself is the unchanging archē of reality.

Aristotle develops the term in a systematic way. In his Metaphysics, archē refers to the first principle or cause underlying a being, a feature connected to his theory of the four causes—material, formal, efficient, and final. The archē is the source that explains why a thing is and how it comes to be, providing a basis for explanation and explanation of change.

Later, the concept was taken up by Stoicism, where archē (archḗ) can denote the active, governing principle of the cosmos, often identified with a rational order or logos. In medieval and modern philosophy, arché continued to function as a general notion of principle or origin, applied to questions about the foundations of matter, knowledge, and reality. The term remains a common point of discussion in the history of metaphysics.