We were gathered in the basement mirror room, listening to John Kells talk more about yielding and pushing hands.
When someone is pushing you, your first reaction might be to resist and use strength. Of coure, the strongest will prevail. This may well be true. But what happens when you are faced with someone stronger? You lose. It is not possible to guarantee that you will always be stronger than the other person.
However, you can guarantee to be weaker. Always. So you listen, accept, stick and follow the incoming push, introducing a subtle turn. The other person suddenly finds themselves in a disadvantageous position.This won't work if the other person is not committed to pushing you.
What appears to be weakness leads to a position of strength. Weakness is an act of transformation. This principle is not unique to T'ai Chi and can, for instance, be found in Judo or Aikido.