Tai Chi is, amongs other things, based on Taoist philosophy, the Five Elements theory and the Eight Trigrams or Bagua (as can be seen in the I Ching or book of changes). Each generation of practitioners are expected to scrutinise and improve on what they have learnt. As a result, every few decades a skilled master will emerge who adapts its practise to the times and ads new insight to its execution. Tai Chi Chuan is therefore a living art form and is forever changing. This is quite a rare quality in a world where we are expected not to question anything and just accept what is dished out to us.
There are many schools of Tai Chi and their practise frequently appears quite varied. However, the underlying principles of natural movement and meditation are common to all (or at least should be). Once these principles are understood and can be executed they can be applied to other forms of ‘internal martial arts' and to all aspects of life such as art, science, philosophy, work etc. The influence of Tai Chi Chuan on one’s life is subsequently much broader than just self-defence.
Tai Chi is the synergistic practise, integration and interaction of three subjects namely: Meditation, Martial Arts and Health. Each is essential for the realization of the other. The meditational aspect is achieved through one pointed concentration often called "keeping in one". The health aspect is the result of beneficial effects to the nervous system and metabolism, the harmonising of breathing and circulation as well as the harmonising of the function of muscles with the internal organs. The martial aspect becomes more prominent when the other two aspects are functioning properly. Knowledge gained from self-defense then feeds back into the practise.