Hui-ssu

By concentration is meant to know that all dharmas (elements of existence), from the very beginning have no nature of their own. They neither come into nor go out of existence. Because they are caused by illusion and imagination, they exist without real existence. They are only the one mind, whose substance admits no differentiation. Those who hold this view can stop the flow of erroneous thought. This is called concentration. (pg. 398, from "A Source Book in Chinese Philosophy," translated and compiled by Wing Tsit-Chan)