Ten years after our 1990 book was published, the first author tried to integrate these results (Locke, 2000). My conclusion was that all goal effects are mediated by task knowledge. Motivation without cognition is useless. Motivation may energize a person, but such an individual will not be able to get anything done unless the person knows how to do so. Conversely, cognition in the absence of motivation is also useless because the individual will have no desire to act on what is known. I suggested that the inconsistent results in the literature were a result of either not measuring all the relevant knowledge or of people acting on their knowledge motivated by factors other than their task goals.