The Buddha's sermon on the Four Truths has been called the First Turning of the Wheel, and the teaching of Prajnaparamita has been called the Second Turning of the Wheel. In the traditional formula of the First Truth, suffering is equated with the Five Skandhas, with which it is necessarily co-extensive. But since the Five Skandhas are empty of self-existence, suffering must also be empty of self-existence. But if suffering is empty of self-existence, then there is no self that suffers. Thus, in emptiness there is no suffering, no source of suffering, no relief from suffering, and no path leading to relief from suffering. This is the basis of Avalokiteshvara's interpretation of the Four Truths.