Many historians have focused on these broad cultural spheres and have treated civilizations as discrete units. Early twentieth-century philosopher Oswald Spengler, uses the German word "Kultur", "culture", for what many call a "civilization". Spengler believed a civilization's coherence is based on a single primary cultural symbol. Cultures experience cycles of birth, life, decline and death, often supplanted by a potent new culture, formed around a compelling new cultural symbol. Spengler states civilization is the beginning of the decline of a culture as "the most external and artificial states of which a species of developed humanity is capable".