Education has a long-standing practice of turning worthwhile learning goals into lists of bits. One might even say that this practice is the original sin in curriculum design: take a complex whole, divide it into small pieces, string those together in a rigid sequence of instruction and testing, and call completion of this sequence "mastery." Thus writes Grant Wiggins in this article. According to Wiggins, it's unlikely that schools can move beyond such practices until policymakers agree on a sound definition and set of criteria for mastery. Wiggins's proposed definition, which he offers to advance the discussion, can be boiled down to this: The essence of mastery is effective transfer of learning, done with creativity and grace. To assess for mastery, schools must ask students to apply their knowledge and skills to perform authentic tasks. And just as important, schools must decide how well a student must perform these tasks to be considered a "master." Locally developed standards are not sufficient, writes Wiggins--only wider-world standards, such as those developed by the Common Core initiative, can provide valid feedback that can assure students they have attained mastery.