On Investigating the Huatou

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