On Investigating Huatou

Investigating a huatou means investigating a phrase, that is, to clearly understand the true meaning of that phrase. Investigating the meaning of a phrase carries the same sense—wanting to clearly understand the true meaning of that phrase. In the practice of investigation, the surface-level thinking of the mind consciousness is relatively minimal; its mental activity is dominated by deep-level deliberation within the mind. The mind is both focused and deep, capable of probing out the substance and deeper meaning of a phrase. With shallow meditative concentration (samādhi), this cannot be achieved.