Revelation of the Complex
From The Visual Display of Quantitative Information by Edward Tufte:
Design is a choice. The theory of the visual display of quantitative information consists of principles that generate design options and that guide choices among options. The principles should not be applied rigidly or in peevish spirit; they are not logically for mathematically certain; and it is better to violate any principal than to place graceless or in elegant marks on paper. Most principles of design should be greeted with some skepticism, for word authority can dominate our vision, and we may come to see only through the lenses of word authority rather than with our own eyes.
What is to be sought in designs for the display of information is the clear portrayal of complexity. Not the complication of the simple; rather the task of the designer is to give visual access to the subtle and difficult - that is, the revelation of the complex.