Again, what has this to do with me? We are scrutinizing your claims to have developed a theory which would be way ahead of its time, not whether I can answer your questions about a dog's behaviour. Yet, to answer your question, indeed: i do not know why or even if a dog chases the mailman. I can speculate that the dog perceives the mailman, entering what the dog thinks of as its territory, as a potential threat and it responds with an attempt to scare the threat off. Whether this hypothesis is actually true, I can not tell. It only reaches a certain point of credibility, if I arrange a set of experiments of which the results would hopefully eliminate other prevalent theories on the subject and support my own.