as "everything which actually happened, whether known, or written, about by historians or not". 6. Periodization It follows from all of this that periodization, the dividing of the past up into the eras or periods, has no a priori existence. It is simply an analytical tool of historians. A periodization which makes sense for the West, will not make sense for Africa or Asia. A periodization which makes sense for economic history, may well not make sense for social or political history. 7. Primary and Secondary Sources The only way we can have knowledge of the past is through studying the relics and traces left by past societies, the primary sources. Primary sources, as it were, form the basic "raw material" of history; they are sources which came into existence within the period being investigated. The articles and books written up later by historians, drawing upon these primary sources, converting the raw material into history, are secondary sources (pedants insist on pointing out that secondary sources may become primary sources for still later historians, but this is a matter of such triviality as scarcely to be worth bothering about). The distinction between primary and secondary sources is a critical one, though no historian has ever pretended that it offers a magic key to the nature of historical study, or that primary sources have a necromantic potency denied to secondary ones. There is always some excitement about being in contact with a genuine primary source, but one will not learn very