This Science of Success is the intelligence gathered by observers over the course of time. It is the laws and theories that appear to be at play in the gaining of success or failure to acquire success, according to the observable senses.
Scientific observers or behavioral scientist are those people who take it upon themselves to analyze the tendencies of certain people and make judgments and predictions based on the outcomes manifested in the observed specimens lives.
Napoleon Hill and his book, Think and Grow Rich is marvelous teacher and textbook on the Science of Success.
If we desire success we need teachers who have done the hard work for us in our lives. Mr. Hill had done the difficult work for us. From here we study the textbook and study to understand the lessons from the teacher.
When it comes to teaching success we might as well call them coaches on how to have a successful life. We would call Mr. Hill a Life Coach today.
If there is a followable path to success then we there are right thinking and actions to keep us on said path. Everyone has a personal path because we're all starting from a different point mentally, physically and spiritually, but Napoleon Hill teaches us to take notice of what successful people have in common in the manner of thought, belief, and action.
Think and Grow Rich teaches us if we follow the example of successful people on certain behaviors, thinking processes and work ethic we are essentially using the Science of Success.