In her 1914 book Una Mary: The Inner Life of a Child, Una Hunt, the daughter of geologist Frank Wigglesworth Clarke, set out to describe the subjective world of her young girlhood. Here’s an example — she had created an imaginary land she called My Country in which her alternate self, Una Mary, lived, and then established it in the Persian rug in the parlor, where her chessmen could play out their adventures: A very yellow palm-leaf in one corner of the pattern was the Holy Land. I thought it was holey, full of holes. I had simply heard some...