This does not, however, provide an answer to the much more difficult question of determining how well a model must agree with observations before projections made with it can be deemed reliable. (drtimball.com)
It proved incapable of asking difficult questions about life's meaning in the face of suffering, much less answering them. (christianitytoday.com)
However, I've found it to be one of the most difficult questions for authors to answer, which in turn, creates a fundamental book marketing problem. (jwikert.typepad.com)