A mathematician and an engineer are sitting in on a string theory lecture. The engineer is struggling, while the mathematician is swimming along with no problem. Finally the engineer asks, "How do you do it? How do you visualize these 11-dimensional spaces?" The mathematician says, "It's easy: first I visualize an n-dimensional space, then I set n equal to 11."

from Computational Complexity and the Anthropic Principle by Scott Aaronson