The most common response I've found to this question is always descriptive, such as, “T'ai Chi is a set of continuous flowing movements combined with deep breathing”, or, that “T'ai Chi is an internal martial art that bases its theory on the Taoist concept that softness will overcome hardness”, or even that “T'ai Chi is simply a method of Chinese exercise that incorporates deep breathing with meditation”. All accurately descriptive, but unfortunately not very informative. The first description could be used to describe quite a few activities, like Ballroom Dancing, Figure Skating or even some Gymnastics. The second description could be used to cover Hsing I and Ba Qua and other various forms of Martial Arts, and the last description is also applicable to Yoga and various forms of meditation. Maybe it would be better to ask this question,
What constitutes T'ai Chi? Or what makes T'ai Chi so totally unique and individual compared to all other forms of movement and action?
The answer to this question is in the way that T'ai Chi views the creation of strength, movement, speed, power and health, and how all these concepts are all tied together through the philosophy of Taoism. T'ai Chi is the only form of movement I know that doesn't use muscle contraction to generate movement and power. I find people have a hard time coming to terms with this concept, and an even harder time believing that muscle has so little to do with the creation of strength. Both these points sound very contentious, but are nevertheless true. This I shall prove to you in the following chapters. T'ai Chi is derived from Taoism, therefore logic dictates that T'ai Chi is in essence a physical manifestation of the principles of Taoism. To understand T'ai Chi, you would need at least some basic understanding of Taoism.
If you were to read up on this topic you would inevitably encounter the Tao Te Chinge (The Book of the Way) by Lao-Tzu (604-531BC). At first glance some of the concepts of Taoism appear quite contradictory, such as "non action creating action", "softness overcoming hardness", "the Tao that can be spoken of, is not the true Tao". At best they seem to be a puzzle, or a riddle, teasing us to inquire deeper into their true meaning, or at worst they are a contradiction in terms and have no other purpose than to cause frustration and annoyance, and are of little relevance to the modern world in which we live. T'ai Chi is the best chance we have to show the amazing principles of Taoism in practice through movement, rather than something to be studied in a intellectual and academic vacuum. I remember being in a group of students watching my Grandmaster of Kung Fu playing his T'ai Chi form, when someone asked him after finishing, “Why does it take 20 to 30 years to master T'ai Chi?”. His answer was, “It doesn't take 20 or 30 years to master T'ai Chi - it takes 20 to 30 years to realise T'ai Chi”. The implication of this statement is that T'ai Chi principles are everywhere, including within ourselves and how we interact in this world. It just takes time to realise that these principles are in effect, everywhere.
Essentially T'ai Chi is not a movement, or even a sequence of movements, T'ai Chi is a principle of movement based on the theory of Taoism. We can apply this theory to numerous things, such as Health, Meditation, Philosophy, Strength, Power, Speed and the Martial Arts, just to name a few. A person is not necessarily a T'ai Chi practitioner just because they're performing a sequence of techniques from a T'ai Chi form, regardless of how beautiful and balanced that person's form may look. A person is only a T'ai Chi practitioner when they are truly practicing and applying the principles of T'ai Chi, these principles of T'ai Chi being firmly grounded in the fundamentals of Taoism. So we have established that.
T'ai Chi is the Physical Manifestation of Taoism.
A principle of movement, principles that are based on the theory of Taoism. If these movements do not adhere to the principles of Taoism then the movement is in reality no different from any other form of movement that requires muscle to initiate and maintain action..