Begin by explaining the concept of negation to your students. You might like to use the following definition (taken from the Englicious glossary):
A word which typically expresses the contradiction of some or all of a sentence's meaning. Examples of negation include -n't, not, never, not, etc.
Grammatically, negation is marked by the presence of of not or -n't with a verb form, i.e. could not or couldn't. Morphologically, negation is marked by the presence of prefixes such as dis-, un- or non-. Lexically, there are several ways of expressing negation: never, deny, deny, hardly ever, etc.
Next, ask your students to discuss what happens in their mind when they read the following sentences:
One of the effects that negation can have is that it forces the reader/listener to first think of the thing that is being negated, before not thinking about it. In other words: you can't not think about something before thinking about it first! Take the first (classic) example: don't think of an elephant. We have to think of an elephant before we can not think of an elephant.
Considering negation in this way makes it an interesting linguistic feature to study when used in non-fiction texts, especially those that carry a persuading function. For example, consider the following sentence, taken from a speech on the economy by the politician Jeremy Corbyn:
Carrying on like this is simply not sustainable. If we want to reprogramme our economy so that it works for everybody, we must use powers we have to back good jobs and industry here.
As we read (or hear) this, the word not asks us to conceptualise 'carrying on like this' (i.e. with a Conservative government in charge, doing perceived damage to the economy), and then compare that against a version of the world that Corbyn imagines and creates for his audience: i.e. one with a Labour government in charge, doing perceived good to the economy.
With that in mind, let's see how negation works in other types of texts.
On the handout (available to download as an attachment at the bottom of this screen) are a number of texts, each which feature a large amount of negation. Ask your students to complete the following questions:
Think critically. What kind of political motive does the writer have for using negation? What kind of alternative realities is the reader asked to imagine through the use of negation?