Zen masters, in echoing the theme of emptiness, like to agree with existentialist thinkers that "life" has no meaning or reason. The Heart Sutra uses the methodology of negation as a way of pointing to this lack of any inherent meaning or reason in the phenomenal world, including the world of the mind. It takes each of the existents, holds it up under an unflinching gaze and declares it to have no sustaining self-nature. This is the wisdom teaching of sunyata of the Mahayana tradition. But, at the same time, compassion is the other and equally important teaching of Mahayana. How do we then bridge the gap between sunyata as ultimate reality and the conventionality of human condition? The existentialist thinkers agonized over this problem and were led to despair and anarchy. In Mahayana, compassion, which is a natural, unforced by-product of a deep state of meditation, supports the wisdom of emptiness, yet allows the individual to have empathy with the conventional appearance of the world without getting lost in it. It may be that compassion works best as a post-enlightenment existential crisis, but nontheless without compassion as a guiding paradigm, the unrelenting precision of sunyata can make life unbearable.
Zen masters insist that our true freedom lies in the choices we make, and each one of us has the power to change "no meaning" into Great Meaning, "no reason" into Great Reason. This is possible because in the pure experience of sunyata, one realizes that one is intrinsically endowed with Buddha-nature and that this Buddha-nature in oneself is not different from Buddha-nature in all living beings. To see others as separate from oneself is to live in delusion and deny one's own Buddha-nature; to see others as sharing in one's own Buddha-nature is to affirm one's essential humanity. In making the free choice of compassion for all beings, we are doing no more than giving expression to our own Buddha-nature. It is only in compassion (Sanskrit: karuna) that wisdom (prajna) finds its fullest expression.