It is necessary to distinguish various sutras. Some are definitive; others require further interpretation.
Definitive sutras are the wisdom sutras, such as the Heart of Wisdom Sutra, in which the Buddha spoke of the ultimate nature of all phenomena, and the Tathagata Essence Sutra from the third turning of the wheel. This is the scriptural source for Maitreya's Uttaratantra and Nagarjuna's collection of praises.
Interpretable sutras cannot be taken literally or at face value. An example is the Guhyasamaja Tantra, wherein the Buddha says that the Tathagata (the Buddha) is to be killed, and that by killing the Buddha, you will be able to achieve supreme enlightenment. Similarly, in certain sutras, it is said that one must kill one's "parents". "Parents" here refers to contaminated actions and attachment, which result in future rebirth.
Madhyamaka-Prasangika proponents speak of phenomena as being empty (having an empty nature). This does not mean phenomena do not exist at all. They just do not exist by themselves, in and of themselves, inherently. Because phenomena possess the characteristics of existing and occurring and are dependent on other factors..., they are devoid of an inherent independent nature. When Madhyamaka-Prasangika proponents speak of emptiness, they speak of the empty nature of phenomena in terms of dependent origination. This view of emptiness through reasoning of dependent origination is very profound: it dispels misconceptions of the two extremes, nihilism and existential eternalism. In Nagarjuna's Mulamadhyamakakarika (Fundamentals of the Middle Way), he says that in a system where emptiness is not possible, nothing is possible. "Since there is no phenomenon that does not arise through dependence, there is no phenomenon that is not empty."
Source:
The 14th Dalai Lama. The World of Tibetan Buddhism: An Overview of Its Philosophy and Practice (Boston, MA: Wisdom Publications, 1995). pp.41-46.
