avoidance: the first line of self defence
When true martial skill is achieved in Taijiquan, it is one of the most effective self defence systems there is. However, it is also true that this level of skill takes years of dedicated practice to achieve. But before this level is reached, there are other skills that can be aquired that do give some protection from surprise or confrontational situations.
By this I don't mean confidence in one's body image, although that may also improve. What I am referring to is a kind of presence in the body, and a feeling of strength and power in the body, that in my experience develops in dedicated practitioners of Taijiquan. Someone will hold themselves in a different way, standing taller and walking with more confidence and purpose. It is these kind of subtle signals that can mean the difference in becoming a target, or a potential assailant moving on.
A consistent practitioner will also develop an alertness and attentiveness to situations and their surroundings. Being less lost in thought patterns gives a heightened awareness of what is happening and who is around them. This means the person will be less likely to unconsciously put themselves in a vulnerable situation. And again, endows the person with a certain quality of presence and confidence that could mean not getting targeted.
An alert and mindful person is also less likely to panic, and to stay alert during a confrontation.
developing real skill
first stage: defensive
While it takes many years to develop fully formed self defence skills in Taijiquan, some basic defensive skills can be developed much sooner.
Taijiquan is primarily a grappling art, and as such develops excellent balance and 'rooting' or steadiness on the feet. The importance of being able to stay one one's feet was seen in early MMA competition, when many martial artists were easily taken to the ground where they were very vulnerable.
This ability to not get taken to the floor could make all the difference. Giving someone the opportunity to run away.
second stage: defense and attack merge
Once all the fundamental skills of Taijiquan are well developed, then defence and attack merge into a single, unified action, using the assailant's impulses against them. This video gives a rare opportunity to see Master Wang demonstrating Taijiquan applications. Notice the energy release or 'fa jin' that he achieves over short distances.