The zen philosophy described in the text Wu-Men goes hand in hand with that of the text the Diamond Sutra.  the focal point of meditation is to be on the word MU and only on the word MU.  Meditation on the word MU will cut off the mind road and allow access through the barrier of the ancestors.  One way in which the this Zen philosophy deviates from that of the Diamond Sutra, is that it calls the mind to focus on one thought, MU, while in the Diamond Sutra the mind is called to not be called and therefore not the think of anything.  Secondly Wu-Men goes say that if attained the attainer will reach a point where they will see and hear the same as all the great ancestors of the ages.