"In solving a problem of this sort, the grand thing is to be able to reason backward" Holmes explained. "That is a very useful accomplishment, and a very easy one, but people do not practice it much..." Most problem solvers reason forward from cause to effect. They brainstorm root causes by asking, "What could be the root causes?" Then they start guessing, which is slow and ineffective. This approach rarely finds every root cause, so it rarely develops complete solutions. The best strategy reasons backward from effect to cause, using Sherlock Holmes' strategy of observation and deduction. Problem solvers ask, "What is different when problems occur?" Reasoning backward is four times more effective than reasoning forward. One set of problem-solving tools based on Holmes' strategy delivers superior results, but it is not well known. This book introduces Holmes' strategy and these tools for the first time. Now, anyone can become an exceptional problem solver.