The Emptiness teachings are the core of Mahayana and Zen Buddhist understanding and practice. Emptiness refers to the reality that nothing is permanent, everything comes and goes in a flash, and hence everything and everyone is "empty of self-nature," that is, any abiding, substantial essence. So things are empty of themselves, but full of everything else. As Nagarjuna teaches, emptiness is interconnection. Because of this, things cannot ever be separate from one another. Our experience of separation, while important, is essentially linguistic; it is fundamentally spurious – though it is, not incidentally, the root cause of our suffering. As Norman says in his short essay, "A Few Words about Emptiness," "Three attitudes arise as a consequence of the appreciation of emptiness: First, flexibility - since nothing is real, fixed, separate, or able to be possessed what's the point of resistance? Second, kindness - since everything is nothing but connection kindness is natural. Third, humility - who is going to feel like he's master of all this talk?" Emptiness and Compassion are the twin pillars of the Mahayana and Zen teachings. You can't appreciate emptiness without appreciating compassion, and vice versa. The Heart Sutra, chanted daily in Zen monasteries and temples, is a great place to begin studying the Emptiness teachings, followed by the Diamond Sutra and Nagarjuna's Fundamental Verses on the Middle Way.