What Is Initial Application? What Is Sustained Application?

Vitakka is the search without a specific target, akin to shining a flashlight around, moving noticeably and rapidly. Vicāra occurs after this broad search, when a general target is found, and attention becomes focused on observing that target, moving subtly and slowly.

When investigating Chan, after identifying a general direction and focus of investigation, one begins to lock onto a target for observation and examination, with the mind becoming more meticulous and difficult to detect.