Before becoming the Buddha, the Buddha is said to have lived 500 lives as a Bodhisattva. That is, as a compassionate, loving, and wise being who seeks the liberation from suffering of all other beings.
In the Lotus Sutra, [probably the most influential of all of the sutras for Chinese Buddhism, and hence Zen] it is said [by implication] that all beings will become Buddhas. It might be at an inconceivably distant time in the future, but all beings, without exception, even the least promising ones, will become Buddhas.
If you, albeit in the very, very far future, are going to become a Buddha, that’s the most important thing that could ever possibly happen to you. In a sense everything prior to that, including your life now, pales into insignificance.
So in a sense, if you’re going to become a Buddha at some point in the future, you’re already a Buddha now. Thus we have the Chinese doctrine of the Universality of Buddha Nature which became an established feature of Chinese Buddhism prior to the formation of the Zen School in the 8th century.
Furthermore, if every being without exception is going to become a Buddha, then every being without exception is a bodhisattva now. That doesn’t mean you’re a bodhisattva, it means that all beings you encounter are bodhisattvas.
All beings are teaching you.
This is the opposite of the spiritual inflation which is implied by thinking of practice as being a means by which you advance towards Enlightenment: you gradually elevating yourself out of the grime of the world and the unwelcome company of ‘unevolved’ beings. It’s the opposite. All beings, all the time, are teaching you, are moving you further towards your eventual Buddhahood. The world is not mud, but light.
They may be teaching from their wisdom; they may be teaching from their stupidity; they may be teaching from their love; they may be teaching from their hate; they may be teaching from their ignorance; they may be teaching from their antagonism towards you. It doesn’t matter: it’s all teaching.
It’s all compassion.
Contemporary Zen people are often quite embarrassed by apparently archaic talk of Buddha Nature. So we just get a lot of chuntering on about being ‘present’ and ‘grateful’ and ‘here and now’. It’s Hallmark Zen. But the fact is, whether it seems ludicrous or not, if you can accept, even for a moment, that this is true—Everything Changes.