"Heraclitus, a nobleman from Ephesus (ca. 500 B.C.), was the first to identify the concept and give it definition as “that universal principle which animates and rules the world.” Primarily identified with fire, it could also mean word, thought, and imagination. In the nineteenth-century, German philosophers had understood Heraclitus’ Logos as one of four Greek rivals for the Urstoff (the primary matter), along with water, earth, and air. Perhaps most importantly, though, Heraclitus identified the Word as Reason, a Reason that rules the universe. Later, Galen, the great Greek philosopher and physician of the Roman empire described the Logos in the following terms: He “did not make the world as an artisan does his work, but it is by wholly penetrating all matter that He is the demiurge of the universe” [Galen, “de qual. Incorp.”]. Plutarch wrote that the Logos was a “go-between” between God and man. The Christian theologian Tertullian argued that the Logos mixes with the matter “as honey does the honeycomb.”
Long after Heraclitus wrote, the Stoics—under Zeno and Cleanthes—adopted the Logos as their “god”: the natural law that holds together and rules the world. Through it and its greatest gift, reason, all human beings possessed dignity. To violate the natural law, to attempt to thwart the Logos, was a grave sin."