User:ToBeFree/PSTS example

How to classify a source
Imagine that an army conquered a small country 200 years ago, and as a Wikipedia editor you have the following sources:
 * a proclamation of victory written at the time of the conquest,
 * a diary written by someone who lived at the time and talks about it,
 * a book written 150 years later, that analyzes the proclamation,
 * an academic journal article written two years ago that examines the diary, and
 * an encyclopedia entry written last year, based on both the book and the journal.

Both the proclamation and the diary are primary sources. These primary sources have advantages: they were written at the time, and so are free of the opinions and fictions imposed by later generations. They also have disadvantages: the proclamation might contain propaganda designed to pacify the conquered country, or omit politically inconvenient facts, or overstate the importance of other facts, or be designed to stroke the new ruler's ego. The diary will reflect the prejudices of its author, and its author might be unaware of relevant facts.

The book and the journal article are secondary sources. These secondary sources have advantages: The authors were not involved in the event, so they have the emotional distance that allows them to analyze the events dispassionately. They also have disadvantages: In some topic areas the authors are writing about what other people said happened and cannot use their own experience to correct any errors or omissions. The authors may be unable to see clearly through their own cultural lens, and the result may be that they unconsciously emphasize things important to their cultures and times, while overlooking things important to the actual actors.

The encyclopedia article is a tertiary source. It has advantages: it summarizes information. It also has disadvantages: in relying on the secondary source, the encyclopedia article will repeat, and may accidentally amplify, any distortions or errors in that source. It may also add its own interpretation.

This sort of simple example is what the source classification system was intended to deal with. It has, however, been stretched to cover much more complicated situations.