In the pursuit of knowledge, inner alchemists often tap into certain wells of information found in the world at large. These wells are deep fonts of knowledge, and to access them, we seek what I call “keys.” I’ve discussed these keys in my writing, describing them as starting points or portals that lead to deeper reservoirs of wisdom. Recently, while responding to a reader’s comment, I was prompted to provide the starting point for a particular key—one that unlocks ...