What is the best way to evaluate a historical source?

There are a number of ways to evaluate a source, and by using a range of these you can get an excellent idea of whether it is reliable or not.

When was it written?- Often public opinion on certain people or events changes depending over time. For example, if a source is being very positive about someone but was written just after they died, this may simply be due to showing this person respect as they have just died, but may not be an accurate representation of them 'in real life'.

Who wrote it?- Certain people will have different opinions on people or events and this may produce bias in what they write. For example if a source is negatively portraying Henry VIII, but was written by someone you know disliked him then this source may also be biased and unreliable as this person is very likely to portray him in a negative light.

Does the source have a purpose?- This is particularly useful when analysing items such as posters and photographs. For example, recruitment posters during the First World War were very positive about fighting in the war and being a soldier, but this may just have been because they had the PURPOSE of encouraging men to sign up to fight, therefore does this really suggest that being a soldier was a good experience, or is this source just biased by its purpose?

Does it add up with what you already know?- When reading a source always ask whether it confirms what you already know from your own knowledge. If a source uses facts you know are true, this makes it more reliable as it seems less likely that it is biased or written with a purpose.

Once you have looked at these key details it may be useful to draw up a brief table of positive and negative evaluation points that you have and see how many you have for each which should help you to decide whether a source is really reliable or not.