Tufte tied this point to computer interfaces, saying that computer interfaces show information stacked in time as you proceed sequentially from one screen to the next. Often people need or want to compare the current visible state to the previous visible state, but can't access the previous state. He suggested we all go out and buy great big high resolution monitors that would allow more comparisons within the eye span. Use small multiples. With small multiples you can escape the problem of only two dimensions and also index on time.
Small multiples have high resolution, they are adjacent in space and easy on the viewer.
Once the viewer has learned how to read one picture they can use that knowledge for all the remaining images. Basically the principles that are important arranging design displays are the same as in analytical thinking. He emphasized that the principles of information design are important regardless if the display technology is the web or a map carved into a rock. Here Tufte went through each chapter in his new book highlighting things of particular interest. Images and Quantities Watch for reshaping of content by form.