Either I can visualize them, and then they're thoughts I can think, or I can't visualize them, in which case the exercise doesn't help me.
If you can, replace 4 with N for sufficiently large N.
If you can't, imagine a creature that evolved in a 4-dimensional universe. I find it unlikely that it would not be able to visualize 4 dimensions.
Here's the new thread for posting quotes, with the usual rules: