On the explanation of the external world based on internal events. It's the great philosophical debate of "how can we really know what we know" and all that jazz.
This is great! And so true. We get so wrapped up in words like "science" and "history" like they're absolute fact, and we forget that everything we've ever learned and that we think we know is just a story our species tells itself. Easy to follow and visually appealing as well--reminds me of a lava lamp.