AI's hardest problem? Developing common sense

Artificial Intelligence has seen radical advances of many kinds over the last years, roundly beating human champions in games like Go and poker that once seemed out of reach. Advances in other domains like speech recognition, machine translation, and photo tagging has become routine. Yet something foundational is still missing: ordinary common sense. Common sense is knowledge that is commonly held, the sort of basic knowledge that we expect ordinary people to possess, like "People don't like losing their money," "You can keep money in your wallet," "You can keep your wallet in your pocket," "Knives cut things," and "Objects don't disappear when you cover them with a blanket." Without it, the everyday world is hard to understand; lacking it, machines can't understand novels, news articles, or movies.