““I have already mentioned two features that successful unifications tend to share. The first, surprise, cannot be underestimated. If there is no surprise, then the idea is either uninteresting or something we knew before. Second, the consequences must be dramatic: The unification must lead quickly to new insights and hypothesis, becoming the engine that drives progress in understanding. But there is a third factor that trumps both of these. A good unified theory must offer predictions that no one would have thought to make before. It may even suggest new kinds of experiments that make sense only in light of the new theory. Most important of all, the predictions must be confirmed by experiment. These three criteria-surprise, new insights, and new predictions confirmed by experiment-are what we will be looking for when we come to judge the promise of current efforts at unification.””
