In his The Course of Positive Philosophy, Auguste Comte famously divided the history of societies up into three main periods. These periods are said to be characterized by their manners of explaining the causes of human experience. The first is the theological phase. In this stage, causes are explained primarily in terms of gods or a god. Then, in the "metaphysical" stage, abstract notions are used to explain the causes of things. Finally, in the "positive" stage, only "positive" (or posited) facts and scientific observations are the primary mode of explanation. Comte thought the final type of society was the highest and most developed. By doing so, he set up his own time's philosophical conception of knowledge as the pinnacle of human thought.