There is a scientific term for this way of thinking—"theory of mind." It's perhaps easiest to grasp the concept when considering how we struggle to make sense of someone else's bizarre or unexpected behavior. If you've ever seen an unfortunate woman at the grocery store wearing a midriff-revealing top and packed into a pair of lavender tights like meat in a sausage wrapper, or a follicularly challenged man with a hairpiece two shades off and three centimeters adrift, and asked yourself what on Earth those people were thinking when they looked in the mirror before leaving the house, this is a good sign that your theory of mind (not to mention your fashion sense) is in working order. When others violate our expectations for normalcy or stump us with surprising behaviors, our tendency to mind-read goes into overdrive. We literally "theorize" about the minds that are causing ostensible behavior.
The evolutionary significance of this mind-reading system hinges on one gigantic question: Is this psychological capacity—this theory of mind, this seeing souls glimmering beneath the skin, spirits twinkling behind orbiting eyes, thoughts in the flurry of movement—is this the "one big thing" that could help us finally understand what it means to be human? Could it tell us something about how we find meaning in the universe?
As a human being, you're prone to overextending your theory of mind to categories for which it doesn't properly belong. Many people remember fondly the classic film Le Ballon Rouge ("The Red Balloon," 1956) by French filmmaker Albert Lamorisse, in which a sensitive schoolboy—in reality Lamorisse's own 5-year-old son, Pascal—is befriended by a good-natured, cherry-red helium balloon. Absent dialogue, the camera follows the joyful two, boy and balloon, through the somber, working-class streets of the Ménilmontant neighborhood of Paris, the glossy red balloon contrasting sharply with the bleak old-Europe atmosphere while adults, oblivious to the presence of an inanimate object that has apparently been ensouled by an intelligent gas, are largely indifferent, even hostile, to the pair. Eventually, a mob of cruel children corners the boy and begins pelting the "kindhearted" balloon with stones, ultimately popping it.