If you have found relevant archival documents, you need to determine their credibility. Assess the value of the information they contain by applying ‘source criticism’.

We distinguish two types of source criticism:

1. External source criticism is concerned with the source’s authenticity (Is this Hitler’s real journal?). Most historians will not have to deal with this very often. Below are a few different approaches:
   • Textual criticism pertains to the contents of the original text. When a source turns out to be a copy, the historian searches for the original wording.
   • Authenticity or provenance criticism establishes whether the purported author, date and geographical origin of a text are accurate.
   • Derivation criticism examines whether the author personally worded the text or copied it from others.
2. Internal source criticism evaluates a source’s information value and is as such extremely important to historians. There are countless questions you can ask about any source. Below are a few different approaches:
   • What is the exact meaning of the statement (words) used in the source? What precisely is the author trying to convey? Do we fully understand the expressions, metaphors and figures of speech in the text? This is relevant not only to 17th-century vocabulary, but also to words we use whose meaning has changed over time (interpretative or exegetic criticism). Take the word ‘soldier’ for example. These days, a soldier is someone who serves in an army. In the Middle Ages, the word soldier referred to anyone who collected pay (Old French sol, soud, sou, from Latin solidum, soldum) for services rendered. So even if you think you understand a word, it may have had different connotations at the time it was written.
   • Does the source’s author actually have first-hand experience of the facts? How and through which agent or media did the author learn of the facts described in the text? Look at the author’s biography: is it plausible s/he witnessed the events s/he described? (credibility criticism)
   • How competent is the author? Is s/he sufficiently knowledgeable about the topic s/he discusses? (competence criticism)
   • What were the author’s motives? To what end was the text written? Which hidden agenda might this source have? These questions pertain to the author’s/source’s position and the circumstances under which the text was written. For example, a description of a resounding electoral victory in a country under totalitarian rule must be analyzed and interpreted in light of that regime (criticism of orthodoxy).

Data

Data must also be approached with a critical attitude. This applies not only to existing data, but also to the data your own research generates. Moreover, processing data is no simple matter. It is an acquired skill for which you need to study the auxiliary science of statistics and consult good statistical manuals.

Be extremely careful in interpreting and presenting statistical data. Always subject data to both external and internal source criticism.