Synthetic intelligence (SI), sometimes referred to as engineered intelligence, is a refinement of the concept of artificial intelligence (AI). SI recognizes that although the capacity for software to reason may be manufactured, it is nonetheless real intelligence and not just an imitation of how human beings acquire and apply knowledge and skill.
John Haugeland, who coined the term synthetic intelligence, uses the analogy of synthetic versus artificial diamonds to explain the concept. Unlike a simulated diamond, which is an artificial stone whose appearance mimics a diamond, a synthetic diamond is a true diamond with all a natural diamond's properties, even though it is manufactured. Both engineered diamonds and engineered intelligence are real, and should be acknowledged as such.
Traditional applications of artificial intelligence have often relied upon software that simply mimics human intelligence by replicating simple human thought processes. Haugeland refers to this approach as GOFAI (good old-fashioned AI). SI software goes beyond simulation, taking advantage of the ways that machines acquire and apply knowledge and abilities at both digital and mechanistic levels.
See Sam Spaulding's TEDx talk, How AI is changing the way we view the world, intelligence and ourselves: