Tai chi is a holistic movement and it's not like reading that you can either sit on the ground or lie down on your bed. When you practice tai chi, you have to treat your body as a whole unit. No part leave behind when you make a move. So I need to make sure your postures are CORRECT.

Probably that's the most obvious way to judge if someone is practicing tai chi or not. But is it so ? The answer would be "yes but not yet". For example, the 56-posture-chen-style form you may want to learn has many movements that are fast and powerful but I have to tell you that the chen style tai chi is the origin of all the other 'easy, soft and slow' tai chi you see today. So what I'm trying to explain here is how to approach an effective way of being benefited from practicing tai chi.

There is no better way for you to obtain an accurate skill by understanding why you should do so. And that's also the profound meaning of 'skill', or it is nonsense.