The Form is a String of Pearls, not a Whip
One thing that students sometimes get hung-up on is the idea that the form is one continuous complex set of moves that flows organically in one specific way. To that end, they focus on the transition between one move to another in order. My experience has been that it’s easier for a beginner to treat each individual move as an end in itself. In other words, the set is not one continuous object that one propagates energy through---like a whip. Instead, it’s like a string of pearls. That is to say, each individual move works independently by itself. Indeed, a person should be able to seamlessly transition from each individual move to any other one in the set. The order is irrelevant. That’s why someone who has memorized the entire set can rearrange the order to be able to do it in one four foot by four foot square.
There is no Single Application to Any Particular Move
It’s a common place among martial artists who teach forms to explain to students that a particular move is something like a punch, a kick, a throw, breaking a choke hold, etc. While it’s true that one move in the set may actually be used to do one particular thing, that doesn’t mean that it couldn’t be used to do something else.
The forms aren’t about specific applications but rather learning general principles. These include things like finding your balance point, learning how to activate specific muscle groups that most people can’t consciously control, becoming aware of and then instinctive in where to place your weight, and so on. Moreover, when you do the form properly over a long enough period of time, you learn principles ‘in your bones’ that may have--at best--been nothing more than parroted theories before.
After one has developed a basis in these ‘theoretical elements’ of the moves, then the player will begin to become aware of all the various different ways these principles might be applied as a martial art or self-defense. At this point if they are able to find someone to spar with (preferably many people---a lot from other traditions, ideally), then they will be able to experiment with these different ideas. At that point they are in an entire universe of new learning---.
In Taijiquan the Entire Body is a Fist
A naive person who’s only exposure to martial arts comes from things like boxing or karate might be excused for thinking that the only way someone defend themselves is by punching or kicking. If, instead, their only experience is Olympic wrestling, judo, or, akido might similarly think that it only consists in grabs and throws.
This is because in the modern world each of these arts has become a sports tradition. That means rules have been brought in to protect players from killing or maiming each other while competing. The problem with rules, however, is that people in competition start training to take advantage of these rules when they compete with others. In karate, for example, it’s illegal to kick below the waist in tournaments---for the very good reason that if you kick someone in the knees, it’s very easy to permanently cripple them. As a result, people train to kick above the waist.
The problem with this, however, is that in a life-and-death situation the best place to kick someone is in the legs. Moreover, if someone trains to only kick above the waist and never trains with the idea that someone is going to kick them in the knees, they are going to be at a tremendous disadvantage against someone who has trained to kick opponents there.
The taijiquan form is different. It comes from a time when martial arts were about real fights instead of tournaments. And because taijiquan has primarily been taught purely as a form of exercise and meditation, this means no one has ever purged it of the more ‘nasty’ moves.
There are moves in the set that could be applied as knees to the groin, thumbs crushing a person’s windpipe, elbows to the sternum, punches to the temple, hip throws that direct a person’s head into the ground, etc. None of these would be allowed in any sort of sport because it would lead to far too many deaths and maimings. But in the form they still have the advantage of being useful for meditation and exercise. And, if someone wishes to pursue taijiquan as an old-fashioned form of self-defense, the information is still there for anyone who makes the effort to understand.