ABSTRACT
Is it possible to imagine a four-dimensional geometrical structure?
It is very hard to visualise such a dimension directly. Off and on for some fifteen years, I have tried to do so. In all this time I’ve managed a grand total of some fifteen minutes’ worth of direct vision into four-dimensional space. Nevertheless I feel I understand the fourth dimension very well. How can this be? How can we talk productively about something that is almost impossible to visualise? The key idea is by analogy. The fourth dimension is to three-dimensional space as the third dimension is to two-dimensional space.
