Historicism is a process that examines the impact of local factors on regional developments. In the development of Historicism there has come to be two distinct "types" of Historicist thought: old and new historicism.
Old Historicism explains literary works in terms of the "influence" of history upon them. This influence might take the shape of wars, social upheavals or equally cultural traditions. An Old Historicist therefore would ask such questions of a work as: What are the author's political inclinations? Do we see any reflections on historical events in this work? What aspects of culture are important to this work? These questions would identify the influence of history on the production of the work.
New Historicism starts off from debating the concept of history and knowledge by asking how we receive our knowledge of history and questioning its veracity as an objective fact. New Historicism therefore argues that what we call "history" is not necessarily "true", but that history is actually a narrative which will exclude some event and characters just as much as it will include others. New Historicism therefore identifies oppressed voices and allows them to have their say in history. These oppressed voices might be women, or working class, or ethnic minorities (such as slaves). New Historicists go beyond this, however, by arguing that, like Old Historicists, all texts are formed by history. The crucial difference lies in that New Historicists believe that the history that influences texts is likewise, only just another text that needs to be interpreted and probed.