The doctrine of emptiness (śūnyatā), then, can be understood as a reaction to scholastic metaphysics, yet the Sarvāstivāda was not the only target of Mahāyāna critique. Many sūtras, while retaining the Buddha‘s original teachings as a backdrop, also seem, in places, to contradict those very teachings. A well-known example of this occurs in the Heart Sūtra's declaration that there is "no suffering, no cause of suffering," and so forth, for the rest of the Four Noble Truths; "no form, no feeling," or any of the Five Aggregates; "no sickness, old-age, or death" or any of the Twelve Links of Dependent Co-origination (nidāna) (PPH; Lopez 1990, 98).
Of course, if verything in the world is empty, then this will include also those oncepts that the Buddha introduced in order to lead his followers out of suffering. In this sense, therefore, emptiness can be seen as a radicalization of the Buddha‘s teachings or as a reflexive extension of their logical implications to those very same teachings. Perhaps this is why the content of Mahāyāna sūtras is rather perplexing, to put it mildly, and appears to contain several internal paradoxes. I shall be claiming that this is also due to the ineffability of ultimate reality.