system
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human
[Avatar TLA / Legend of Korra] What happens when two benders try and bend the same thing?

For instance if two water benders try and bend the same ball of water, or one is trying to freeze it and the other is trying to prevent it from freezing. Does it come town to a contest of will? Or who's bending is naturally more powerful? Or is there some technique involved?
gpt
Bending is a martial art, and like other martial arts it really comes down to the specific strategies used. Imagine two non-benders trying to take a basket from each other. If they're both unskilled, they'll just wrestle over it and either the stronger one will pull it away or they'll just rip it apart between them. A skilled non-bender has a lot of techniques to pull an object out of the hands of a stronger person. Two skilled people will come down to who has the better strategy or possibly to just strength if each knows how to counter the other's techniques. Someone might even wrench an arm if they pull too hard. 

For benders, it's mostly the same. Benders just use their chi as a spiritual connection between their muscles and the natural world. There's no inherent power level, and willpower doesn't enter into it any more than willpower matters to non-benders (that is, willpower determines your tenacity in a physically grueling fight, but it doesn't literally amplify your power). Your chi and your muscles are natural parts of you that can be strengthened by training. 

Unlike muscles, chi is very effectively trained by mental exercises like meditation and certain emotional states--but that's not so different from the focus and mindset that lets a non-bender martial artist execute difficult techniques in the midst of battle. Chi, being an essence connected to all parts of the body, is also influenced by and influences your emotions, so your willingness to feel a certain way can enhance in reduce bending strength.

The third component to bending is your spiritual link to a specific element. Benders have this, non-benders don't. It's pretty much a binary thing. No ordinary person will win a fight over bending a rock because their spirit has a stronger connection to earth. The avatar, in the avatar state, can use the spiritual connection of all her/his predecessors, which multiplies the avatar's capabilities by the number of predecessors.