AI needs to grasp cause and effect - but even humans still have trouble with it. "For his part, Pearl says AI can't be truly intelligent until it has a rich understanding of cause and effect. Although causal reasoning wouldn't be sufficient for an artificial general intelligence, it's necessary, he says, because it would enable the introspection that is at the core of cognition. "What if questions 'are the building blocks of science, of moral attitudes, of free will, of consciousness,' Pearl told me." Brian Bergstein writes in MIT Technology Review.