In shamatha, you are present. At the same time, your mind becomes so transparent, so penetrating and loose, that it becomes like a sieve. You think you are pouring teachings into it, but end up with nothing at all. If the buddhadharma were a theistic religion, based on the worship of a deity or savior, and if you thought you knew perfectly what you were doing, your mind would cease to be a sieve and instead become a cast-iron cauldron. That model seems very sympathetic, because one would like to have something very solid and definite to hold on to as opposed to becoming a sieve. But in the nontheistic tradition, your state of being becomes a sieve with which it is difficult to catch or to hold on to anything. Therefore, in order to understand the essence of the teachings, it is necessary to develop constant awareness.