trictly speaking, it is best to realize emptiness before one undertakes the practice of all phenomena lacking self- existence; however, realizing emptiness is not easy since there are many basic requirements such as the preliminaries that have to be completed.

Regardless, one who practices emptiness must at least understand the underlying concept; only then can emptiness be practiced. If we do not even know what no-self or emptiness means, we will not know how to practice emptiness. Hence, prior to teaching the practice of no-self, I shall first explain the principle of “no-self” — why there is “no-self,” that is, why the “self” does not exist. With this understanding, the practice can then proceed.

- Quote from The Four Seals of Dhama, "All Phenomena Lack Self-Existence"