The term “Presocratics” refers to a group of Greek thinkers who lived not later than Socrates and who were not decisively influenced by him. They are often referred to as the first philosophers as they represent the dawn of human speculation in the West. The essay examines the fragments of major Presocratics - Thales, Anaximander, Anaximenes, Heraclitus, Pythagoras, Parmenides, Empidocles and Anaxagoras, which contain their views and arguments as reported by subsequent authors. Although these fragments are incomplete and are based on secondary quotations, it is possible to sift through them and develop coherent and logical interpretations that approximate the original idea and intentions of these philosophers. The aim of this essay is to shed light on the philosophical meaning and significance of the concept of Arche (ἀρχή) – an untranslatable Greek word that connotes origin, principle, first in the series, or source, which constitutes the central thread of speculation among the Presocratics and their most influential contribution to the history of Western thought.