Proper documentation will help you avoid plagiarism and will empower you to:
- Join the "great conversation," in which ideas throughout the world and time are invented, discussed, or refuted.1
- Honor the thinking and intellectual property of other authors, by crediting their work.
- Lend authority to your own contributions.
- Help other researchers find the sources that inspired your work.2
- Avoid infringing an author's legal copyright. Proper citation of a work used in an educational context is a fair use by law, but without citation, the use of the work crosses ethical, and possibly legal, boundaries.
You do not need to document if you're using common knowledge (e.g. the Declaration of Independence was approved by the Continental Congress on July 4, 1776), or if you're using your own thoughts, ideas, opinions, observations, or experimental results.
However, you must document whenever you copy (include a chart or diagram, for example), quote from, paraphrase, or summarize another author's work. This includes information from Web pages, books, songs, television programs, email messages, interviews, articles, artworks, or any other medium.3 A good paper should be composed mainly of your own ideas, citing various sources to support your argument.