Pavlov is perhaps best known for introducing the idea of the conditioned reflex, although Todes notes that he never used that term. It was a bad translation of the Russian uslovnyi, or “conditional,” reflex. For Pavlov, the emphasis fell on the contingent, provisional nature of the association—which enlisted other reflexes he believed to be natural and unvarying. Drawing upon the brain science of the day, Pavlov understood conditional reflexes to involve a connection between a point in the brain’s subcortex, which supported instincts, and a point in its cortex, where associations were built. Such conjectures about brain circuitry were anathema to the behaviorists, who were inclined to view the mind as a black box. Nothing mattered, in their view, that could not be observed and measured. Pavlov never subscribed to that theory, or shared their disregard for subjective experience. He considered human psychology to be “one of the last secrets of life,” and hoped that rigorous scientific inquiry could illuminate “the mechanism and vital meaning of that which most occupied Man—our consciousness and its torments.” Of course, the inquiry had to start somewhere. Pavlov believed that it started with data, and he found that data in the saliva of dogs.