Information sources are created for different audiences, and that can affect both their content and style. For example, an encyclopedia of medicine written for doctors will use different language, style and structure than a medical encyclopedia written for a general audience.
You also need to take into account whether the creator of the information source felt that their intended audience was like-minded or not. For example, a speech about a religious topic given by a preacher to his own congregation will likely be structured differently and use different language than the same speech given by the same preacher to a group of hostile or uninterested strangers on the street. The former might sound like a series of affirmations, while the latter might sound more like an argument, debate or persuasive essay.
It is important to keep in mind the intended effect of an information source, because that can inform what information it contains and how reliable that information is. Also, you should be aware of any effects the information source is having on your emotional state and your opinions.
Common intended purposes for information sources are:
A single information source can have multiple overlapping purposes, which can (sometimes intentionally) mislead readers as to its true purpose. You will learn more about evaluating sources in Chapter 5.