Even though heat and sound are both forms of energy, when you were a kid, you probably didn’t need to be told not to speak in thermal convection. And each time your children come across a stray animal, they likely don’t have to self-consciously rehearse a subroutine of zoological attributes to decide whether it’s a cat or a dog. Human beings come pre-loaded with the cognitive gear to simply perceive these distinctions. The differences appear so obvious, and knowing the differences comes so naturally to us, that we refer to it as common sense. Computers, in contrast, need step-by-step handholding—in the form of deterministic algorithms—to render even the most basic of judgments. Despite decades of unbroken gains in speed and processing capacity, machines can’t do what the average toddler does without even trying. That is—until now.