Plato thought he was considering our understanding of universal forms when he imagined the metaphor of seeing shadows in a cave (cast by a fire onto the cave’s wall, the shadows are only a vague semblance of their true three-dimensional realities). But then we have to wonder, what sort of cave was Plato imagining? And if it was anything like some I’ve known, poor Plato would have been shocked to see what a black light can reveal – glowing minerals that seem to turn the real into something hallucinatory. Of course Plato would have understood the universal nature of the concept of cave, and would undoubtedly have recognized this specimen from New Hampshire (based on Ruggles Mine). Enjoy!