In his talk on design, Chip Kidd discusses the art of first impressions and how to judge design you encounter in real life. The graphic designer mentions the contrasting concepts of clarity and mystery in his entertaining speech and how they are balanced in his daily work and daily life.
Using numerous examples, the talk on design explains when being clear is an effective strategy compared to when you should be mysterious. The speaker explains "mystery demands to be decoded and when it's done right, we really really want to." Another way to be mysterious in design is with what he refers to as the visual vernacular (or making something look like something else). He demonstrates these concepts further with several book covers he designed.
He also shows what unuseful clarity looks like with a Diet Coke campaign.