"No-mind" describes a mind in which there is neither aversion nor desire; one in which there is no self-referential attachment to the phenomena ("forms") of daily life. While one continues to deal with exigencies as they arise in daily life and in the mind, one can deal with them without craving, anger, attachment, or vexation. When we can put down negative mind-states like these, then the mind's natural spaciousness and openness makes it possible for wisdom to arise. When the mind can free itself of all discriminating thought, it is able to perceive the emptiness of phenomena, including the self. One can then experience what the buddha experienced in his own enlightenment.
The story of Huineng's enlightenment (see Lesson 3) illustrates the idea of no-mind. While still a layman, Huineng by chance heard someone reciting from the Diamond Sutra these words:
"Abiding nowhere," refers to a mind that, while it functions, sees phenomena as having no characteristics to which it can attach (and therefore abide). A mind that does not abide is aware of vexations without being repelled or attached to them. When a mind can abide nowhere, it is free to function in its capacity as wisdom. When the activities of the mind are totally without self-reference, free from attachments and free of discrimination, then it is possible for the mind's original wisdom to manifest. "Give rise to [original] mind" means that when the mind has freed itself of attachments and vexations, the original wisdom of mind can manifest. This original wisdom is "seeing one's buddha nature." It may also be called enlightenment.
When Huineng heard these words, he experienced an awakening. He then resolved to find a teacher and joined a monastery where the abbot was the Fifth Patriarch of Chan, Hongren (602-675) who later transmitted the Dharma to Huineng as the Sixth Patriarch. In his teachings, Huineng stressed the "formless" or "no-characteristics" aspect of enlightened mind. All "forms" are associated with phenomena, whether of the external world or of the mind. As such, forms exist in time as well as in space. However all phenomena are interlinked by causes and conditions and co-dependent origination. Therefore all phenomena lack self-identity, are thus empty of self-nature, and are ultimately formless or empty.