Do you think that by watching videos and reading some books a person can actually learn Tai Chi or ...?

Having studied several martial arts for over 41 years, I can only say that books and videos can only give you an idea of how things are done. To use them is to mimic the moves but have no understanding. Books and videos can't correct errors. Those errors could be serious ones that would get you killed in a life threatening situation. Only a competent instructor can teach correctly and fix errors before they become habit. Combat is ever changing. Books, videos, and even real martial arts cles teach by scenarios. One must master the technique, timing, distance, ...tec. then in order for someone to really have self-defense skills, it is necessary to learn how to adapt to any situation in an instant. Things never happen in real fights the way you practice for them. Only much experience can prepare someone for the unexpected things that happen in real fights. Learning form books and videos is at best like trying to become a surgeon by only reading books and watching videos. I certainly would not let anyone that learned that way operate on me.