The way that we talk about existence in English in these conversations that deal with odd questions like "Is a rock arisen due to ignorance?" is in a de facto ontological sense, which, when paired with notions such as "Cars exist independent of a perciever", indicate that "existence" is being framed in a cosmological manner.
Cosmology is refuted via the fourfold negation, in SN 12.48, but it is not refuted on the grounds that reality/cosmos does not exist, or that cosmology "doesn't exist" in any ways, it is refuted because extreme cosmological positions are unrelated to the teaching ("Avoiding these two extremes, the Tathágata teaches the Dhamma via the middle").
Nágárjuna is not a cosmologer. When Madhyamika philosophy negates "inherent existence" they are negating the heretical notion that any reality, real or perceived, is unconditioned, save for Nibbána, views about which, themselves, are conditioned. Arguing against "inherent existence" is arguing that Nibbána and complete perfect realization thereof (samyaksambodhi) is the only thing that is unconditioned. All else lacks "inherency", including form, which is arisen from causal conditions. Note that this does not mean that all form is arisen via dependent origination, it simply means that forms (any forms) are arisen by causal conditions.
Existence is de facto established on metaphysical grounds by statements like "There is, monks, an unborn" (Ud 8.3) as well as numerous other times the Buddha establishes something as existing, and neither Theraváda nor Madhyamika are interested in refuting that.
The notion that anything is uncaused and unconditioned save for Nibbána, like for instance "form", is a very ancient heresy in Buddhist and no contemporary schools of Buddhism (arguably) subscribe to svabháva theories of dharmas other than svabháva of Nibbána.
Yet the Múlamadhyamakakáriká and Nágárjuna's work discrediting the svabháva heresy is still relevant in modern Buddhism because there are still people who claim to be Buddhists who believe that things other than Nibbána are stable, permanent, and unchanging, whether due to reconstructionist arrogance or simply being poorly informed as to the Buddhavacava.
The Múlamadhyamakakáriká is designed to be a litmus test of the alleged permanence of anything other than Nibbána, including most views of/about Nibbána. Everything is denied the status of unconditioned save for Nibbána itself.
I'm taking the liberty of quoting you here, Twilight, rather than in the thread "No Creator in Buddhism", where this quote is from, because I think it is relevant to some misconceptions about "inherent existence" that have been voiced in response to the statements that negate "inherent existence", not necessarily because I think or don't think that you hold such misconceptions:
Twilight wrote:The 5 aggregates that constitute what we conventionally call "a being" exist since forever.
No one is disputing that the 5 aggregates exist, or that they constitute what is called a "being". This is a common criticism leveled at teachings that negate "inherent existence", because it is common to see these Buddhist discourses as nihilistic, or negating existence on a metaphysical level.
The aggregates, though beginingless (but not uncaused), are arisen due to causal conditions and are therefore conditioned, and being conditioned they lack "inherent existence", what they have is a dependent existence, dependent on their conditions.
Like Javi said earlier, if a given Buddhist is informed as to the Buddhavacana and does not ascribe unchanging permanence to anything other than Nibbána, then the Múlamadhyamakakáriká is an unnecessary and possibly redundant text, which merely goes over what is already in the Buddhavacana via the suttas and rearranges the material into a new presentation designed to refute unconditioned existences aside from Nibbána, which was a contemporary heresy of Nágárjuna's time, which was not believed by Buddhists before then, hence why the svabháva heresy is not explicitly mentioned or condemned in the Buddhavacana.
However if a given Buddhist subscribes unchanging permanence to anything other than Nibbána than the Múlamadhyamakakáriká is designed to refute their notions.
Basically, the entire text is an essay against hypostatization/reification/objectification
of any and all things, including Nibbána. Nibbána is uncaused, yet the conceptual framing of Nibbána as "opposite" of samsara is itself arisen via causal conditions
, specifically the causal condition of samsara itself, thus hypostatizations/"mental proliferations" of Nibbána in relation to samsara
are conditioned and are not, themselves, Nibbána. This is the context of the saying
(Mūlamadhyamakakārikā XXV, Nirvānaparīkṣā section)
There is no distinction whatsoever between saṃsāra and nirvāṇa.
There is no distinction whatsoever between nirvāṇa and saṃsāra.
What is the limit of nirvāṇa, that is the limit of saṃsāra.
There is not even the finest gap to be found between the two.
The views concerning what is beyond cessation, the end of the world, and the eternality of the world are dependent [respectively] on nirvāṇa, the future life, and the past life.
It is talking about views/hypostatizations of Nibbána. Hypostatizations of Nibbána are identical, it argues, to hypostatizations of samsara, they are both mere hypostatizations. As hypostatizations arisen via causal conditions, they are dependant on Nibbána, the uncaused/unconditioned, but those hypostatizations are themselves not unconditioned, in fact, they are implied, by Nágárjuna, to also be conditioned by pernicious self-view (What will I be in the future? What was my past self?) ("The views concerning what is beyond cessation, the end of the world, and the eternality of the world are dependent [respectively] on nirvāṇa, the future life, and the past life"). Nágárjuna labels such views as samsaric.