The empirical core of Zen is zazen, or sitting meditation. The primary article of faith in Zen is that by regularly performing zazen one will eventually experience the same direct understanding and awakening the Buddha experienced when he became enlightened. This is not to say that people who do not practice zazen can get nothing out of Zen, or that other practices cannot have similar effects.
The Buddha emphasized the direct experimental approach, encouraging people to see things for themselves rather than just taking his word for things.
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