Within Tendai thought, emptiness (śūnyatā, kū) is not treated as a mere void, but as the absence of any fixed, independent essence in all phenomena. Things lack their own self-nature because they arise only through causes, conditions, and interdependent relationships. This does not amount to nihilism; rather, it highlights that what appears solid and separate is in fact fluid, contingent, and relational. Emptiness thus undercuts both the belief in permanent substances and the despairing view that nothing at all has value or efficacy.

Tendai articulates this vision through the doctrine of the Three Truths: emptiness, provisional existence, and the Middle. Emptiness indicates that all dharmas are devoid of inherent nature; provisional existence acknowledges that, despite this, phenomena still function and appear within ordinary experience. The Middle Truth is the simultaneous validity and inseparability of these two perspectives, a non-dual standpoint that neither clings to being nor to non-being. These are not three different realms, but three aspects of the same reality, perfectly interfused in every moment and every phenomenon.

From this standpoint, emptiness becomes the very condition that allows for transformation and awakening. Because beings and things are not locked into a fixed essence, they are open to change; this openness is what makes enlightenment possible. Tendai links this directly to Buddha-nature, seeing the empty nature of all phenomena as the ground upon which enlightenment can manifest universally. Emptiness, conventional appearance, and the Middle Way perspective thus form a single, integrated vision in which the world is neither denied nor reified, but understood as an interdependent field that can be awakened to its deepest significance.