Historical-biblical criticism includes a wide range of approaches and questions within four major methodologies: textual, source, form, and literary criticism. Textual criticism examines biblical manuscripts and their content to identify what the original text probably said. Source criticism searches the text for evidence of their original sources. Form criticism identifies short units of text seeking the setting of their origination. Redaction criticism later developed as a derivative of both source and form criticism. Each of these methods was primarily historical and focused on what went on before the texts were in their present form. Literary criticism, which emerged in the twentieth century, differed from these earlier methods. It focused on the literary structure of the texts as they currently exist, determining, where possible, the author's purpose, and discerning the reader's response to the text through methods such as rhetorical criticism, canonical criticism, and narrative criticism. All together, these various methods of biblical criticism permanently changed how people understood and saw the Bible.