We can help our readers understand an idea by contrasting it with a related but different idea.
One example, which I’ve already quoted here, is from the start of Stephen Darwall’s book Welfare and Rational Care:
[Welfare is] the good of a person in the sense of what benefits her. This differs … from what a person herself values, prefers, or takes an interest in.
Darwall is distinguishing objective and subjective welfare, and focusing on the former. Making the distinction explicit helps us see what he means.
In my earlier post about ‘non-definition definitions’, I criticised Isaiah Berlin’s lack of clarity over positive liberty. But Berlin is much clearer about negative liberty. One reason is that he distinguishes it from ability: if I cannot understand Hegel, this is a lack of ability, not a lack of negative freedom, because no one has stopped me from understanding Hegel. Further differentiation of these ideas would help: for example, Berlin is not explicit about whether negative freedom and ability are two separate things, or whether negative freedom is one kind of ability. But what he writes certainly gives us a better sense of what he has in mind.
A third example comes from Anita Sarkeesian’s fascinating analysis on the Feminist Frequency website, uncovering subtle and not-so-subtle stereotypes about women and violence in video games. The second video of Sarkeesian’s three-part series (warning: graphic scenes involving violence against women) is here. At 10 minutes 40, when Sarkeesian discusses ‘violence against women’, she states that she means violence which is
linked specifically to a character’s gender or sexuality. Female characters who happen to be involved in violent or combat situations on relatively equal footing with their opponents are typically exempt from this category because they are usually not framed as victims.
The video at this point shows two women fighting each other in a typical Streetfighter-style fighting game. That isn’t violence against women as women; it’s just violence which involves two people who happen to be women but could have been any gender.
By contrasting her notion to a different notion, Sarkeesian helps us understand what she is and isn’t discussing. It’s a simple but effective way of helping our readers see what we are focusing on.