In writing and speeches, supporting evidence is material, such as statistics, instances, and quotes, that assists the author of a book or the speaker of a speech in explaining and proving his viewpoint or argument. Supporting evidence can be used to corroborate facts stated by the author or speaker, to provide additional information about what he is saying, or to challenge assumptions made by him or others. Without supporting evidence, opinions would be no more than subjective beliefs. History is full of people who have done great things or made important contributions without any written records whatsoever. The only way they can be recognized is through other people's words about them, which are called reports. These reports usually contain information not found anywhere else, including descriptions of how they conducted themselves and their ideas on issues before them. For example, historians know about Alexander the Great because people hundreds of years after him wrote books about him. They included details about his campaigns that were not available elsewhere. Similarly, scientists know about Einstein because those who worked with him later wrote articles about him. They described his habits and his views on science and religion for example, subjects about which most scientists then knew nothing. People don't like being told what they do or did not do. This is especially true if they have been dead for a long time.