ONE ERROR IN LOGICAL THINKING
If all these [things] are empty,
Nothing can arise and nothing can disintegrate.
Consequently the Four [Noble] Truths
Will not be there for you.
…And because the [Noble] Truths will be non-existent,
The sublime Dharma will also not be there.
If Dharma and Sangha are non-existent,
How can there be a Buddha?
Nagarjuna pointed out the error by saying that it is due to "not realizing the purpose of emptiness, its nature and the meaning".
Nagarjuna goes on to explain the logical conclusion of the Buddha's teaching of pratītya-samutpādasvabhāva ("self-nature"), and that thus all phenomena are empty of inherent being:
Whatever is dependently arisen
Is explained to be emptiness.
Its existence is imputed in dependence upon something else
And this is the path of the Middle Way (Madhyamaka).
(Gyamtso 2003, 157)
He argued that if people existed in complete independence from other phenomena and had an unchanging essence, they could not come into being, nor could we ever grow or have new experiences. People would either always be in a state of suffering or always in a state of happiness, and that those that are not already Buddhas could never become one.
Nagarjuna was the first philosopher to propose the two-truths doctrine, which postulates that there are two types of truth, the "absolute truth" (paramārtha satya) of śūnyatā, and the "relative truth" (saṃvṛti satya) of appearances.
He argued that the world of names and forms (namarupa) does indeed exist, but only as appearances (ILLUSION), not as something which is substantially real. They are "neither non-existent nor permanent."
In order to understand the true nature of the phenomenal world, people must understand emptiness. Likewise, it is the world of logic and forms that leads people to understand śūnyatā.
Furthermore, without forms there is no emptiness, and without emptiness there are no forms. Thus, even the two truths are dependently arisen. Realization of this is said to lead to direct perception of "tathata" or suchness, as the union of luminosity (ILLUSION) and EMPTINESS.