Three Points

question: 

Could you reduce, in about 3 points, Sun Tzu’s major philosophies about battle and warfare, and how the average person could apply those to work and life?

Thanks for the question, especially since it raises a number of key points itself. 

  1. About Battle: Like Euclid's Geometry, Sun Tzu spends a lot of time defining his terms. Competition is a comparison. A battle is a point of comparison, that is, a specific time and place at which a comparison is made. You want to those "meetings" (the primary meaning of the Chinese term translated as "battle") unless you know you can win that comparison. 
  2. About Warfare: Warfare is the long-term, never-ending process of comparison. There are only two ways to "win" a given instance of comparison (a battle) but there is only one way to win the long-term process. You can win a battle by tearing down the position of your opponent. However, that process also weakens you and inevitably leads to long-term failure. Over time, the only way to win the process of comparison is continually building up your own position so that others want to support you rather than a oppose you or even ignore you.
  3. About Application: Sun Tzu's methods of building up positions works for any process in which people are compared to others, which is every aspect of human society. Those methods can be described as: - Listening to others to understand your positions and surrounding positions, - Aiming at openings, that is, empty places, in the environment to advance your position, - Moving in a way that responds correctly to the nine common situations and uses creativity to win a new position, - Claiming the rewards of your new positions and using them to defend your position as a base for future advance. 

Of course, he has over a couple of hundred specific tactics for accomplishing these four steps.