without changing the text substantively. On the other hand, an editor may suggest or undertake significant changes to a text to improve its readability, sense or structure. This latter type of editor can go so far as to excise some parts of the text, add new parts, or restructure the whole. The work of editors of ancient texts or manuscripts or collections of works results in differing editions. For example, there are many editions of Shakespeare's plays by notable editors who also contribute original introductions to the resulting publication. Editors who work on journals and newspapers have varying levels of responsibility for the text. They may write original material, in particular editorials, select what is to be included from a range of items on offer, format the material, and/or fact check its accuracy. Encyclopaedist Encyclopaedists create organised bodies of knowledge. Denis Diderot (1713–1784) is renowned for his contributions to the Encyclopédie. The encyclopaedist Bernardino de Sahagún (1499–1590) was a Franciscan whose Historia general de las cosas de Nueva España is a vast encyclopedia of Mesoamerican civilization, commonly referred to as the Florentine Codex, after the Italian manuscript library which holds the best-preserved copy. Essayist Essayists write essays, which are original pieces of writing of moderate length in which the author makes a case in support of an opinion. They are usually in prose, but some writers have used poetry to present their argument. Historian A historian is a person who studies and writes about the past and is regarded as an authority on it. The purpose of a historian is to employ historical analysis to create coherent narratives that explain "what happened" and "why or how it happened". Professional historians typically work in colleges and universities, archival centers, government agencies, museums, and as freelance writers and consultants. Edward Gibbon's six-volume History of the Decline and Fall of the Roman Empire influenced the development of historiography. Lexicographer Writers who create dictionaries are called lexicographers. One of the most famous is Samuel Johnson (1709–1784), whose Dictionary of the English Language was regarded not only as a great personal scholarly achievement but was also a dictionary of such pre-eminence, that would have been referred to by such writers as Jane Austen. Researcher/Scholar Researchers and scholars who write about their discoveries and ideas sometimes have profound effects on society. Scientists and philosophers are good examples because their new ideas can revolutionise the way people