‘To look within’ has almost become a trivialized expression in Zen. It is somewhat ironic too. I am going to look within by going to Japan or China. I need to find a teacher to help me look within—I can’t do it myself. To be frank, we are not engaged in looking within when we rely on externalities, even doing zazen which is an attempt to look within.
I know this might seem strange to ask, but what do we hope to find when we look within? Our mental world is not going to change. What changes is that we see, firsthand, the very stuff or suchness of our mental world which also happens to be the stuff the universe is made of. Seeing this way is truly an awakening.
But oddly, if someone were to go into the mind of a Buddha it would be just like their own mind. They would be unable to see or sense this spiritual suchness. As far as their mind reaches is consciousness which might be called the “dualizer” since it relies on the aware subject and an object for it. During awakening, however, subject and object disappear in the time of a finger snap. They are, exactly, one and the same, namely, Mind-only (cittamātra) or the same, Mind-itself. Consciousness we discover is totally dependent upon Mind-only. It is not as fundamental as we imagined previously.
The Lankavatara Sutra says, in fact, “"Those who are attached to the notion of duality (object and subject) fail to understand that there is only what is seen of the Mind."
We are born into such a failure, unknowingly, as a given. From this, all manner of error arises for us. We are constantly self-deceived by consciousness. And what we need to find, namely, Mind-only is totally hidden from us by the workings of consciousness. It allows us to look within, only so far — and this is not far enough.