* Authenticity: Is the letter genuine, or a forgery? Determining authenticity requires examining handwriting, paper type, ink, seals, and comparing it to known examples of the author's writing or the recipient's correspondence. Forgeries can be sophisticated and difficult to detect.
* Bias and Subjectivity: Letters are inherently subjective accounts written from a particular perspective. The author might omit information, exaggerate events, or present a biased view to serve their own purposes (e.g., to persuade a recipient, to protect their reputation, or to influence later perceptions). The historian must be aware of this inherent bias and look for corroborating evidence from other sources.
* Incomplete Information: Letters might not cover the entirety of an event or topic. They might only address a specific aspect or present a truncated version of the writer's thoughts or actions. Historians need to recognize these gaps and avoid drawing conclusions based on incomplete data.
* Selectivity of Survival: Not all letters survive. Factors like physical deterioration, accidental destruction, deliberate destruction by the sender or recipient, or simply loss over time can lead to a skewed representation of events. The surviving letters might not be representative of the totality of correspondence exchanged.
* Interpretation: Even when the authenticity and context are established, the interpretation of a letter's content remains challenging. Language evolves, and the nuances of meaning might be lost over time. Historians must carefully consider the historical context and the intentions of the writer to avoid misinterpretations.
* Attribution: Determining the correct author and recipient of a letter can be difficult, especially if the letter is unsigned, uses pseudonyms, or has unclear addressing. Misattribution can lead to errors in historical analysis.
* Damage and Obscurity: Letters can be damaged by time, fire, water, or insects, rendering parts illegible. The handwriting might be difficult to decipher, especially if it is cursive or in a foreign language. This limits the information available to the researcher.
In summary, while letters offer valuable insights into the past, historians must approach them critically, acknowledging their limitations and biases and employing rigorous methods to verify their authenticity and interpret their content accurately. They often need to cross-reference letter content with other types of historical evidence to create a more complete and nuanced understanding of the past.