Whereas Shen-xui (Northern school) proposes to look at the human mind to find enlightenment, Hui-neng (Southern school) proposes to actually look at our inherent nature underlying the mind.
What Hui-neng means is that the pure mind is that the inherent Buddha-nature is already within each of us. It is deeper than the mind, and it is already pure. Indeed, it is regarded as simple, and like something for a beginner—not complex.
Thus, our true human nature is none other than the Buddha-nature itself. This mind—our own mind—is thus always pure, if only we can realize and accept that fact.