Tracy says that among all the goals you could set for yourself, there is one that matters more than the others. He calls it the Major Definite Purpose. Your Major Definite Purpose — or MDP — is the one goal that, if achieved, would improve everything else in your life. It is the organising principle around which all your other goals arrange themselves. When you identify it and pursue it relentlessly, something remarkable happens to your capacity to achieve. He explains why through a concept called the Reticular Activating System, or RAS. Deep within the brain is an organ Tracy calls the reticular cortex — functioning like a telephone switchboard that routes all incoming information to the relevant part of your awareness. When you send a clear goal message to this system, it begins making you acutely alert to anything in your environment that could help you achieve that goal. His example is vivid. If you decide you want a red sports car and write it down as a goal, you will suddenly start seeing red sports cars everywhere. They were always there. But your brain had not been instructed to notice them. Once it has, they appear on every corner. The same applies to opportunities, people, ideas, and resources related to your MDP. Once your brain is programmed with a clear, specific goal, it starts filtering the world around you for relevance to that goal. Without it, you drive through life in fog. For a Major Definite Purpose to work, Tracy sets six criteria: It must be something you personally and intensely desire. It must be clear and specific — describable in simple words. It must be measurable and quantifiable. It must be believable and achievable given your current circumstances. It should have a reasonable probability of success — at least fifty-fifty. It must be in harmony with your other goals and values. The great question for identifying your MDP: what one great thing would you dare to dream if you knew you could not fail?