To solve a problem or to reach a goal, you don't need to know all the answers in advance. But you must have a clear idea of the problem or the goal you want to reach.
Bio: Martin E. P. "Marty" Seligman is an American psychologist, educator, and author of self-help books. Since the late 90's, Seligman has been an avid promoter within the scientific community for the field of positive psychology.