The claim that everything is empty invites an obvious objection, and the Mulamadhyamakakarika spends much of its length answering it. If nothing has a nature of its own, the objector says, then nothing exists, the Buddha taught nothing, suffering is not real and the path is pointless. Nagarjuna replies that emptiness is not nothingness but a statement about how things exist. They exist dependently, arising in reliance on causes, on their parts, and on the concepts and words that pick them out. A thing carrying a nature of its own would need none of that, and would for the same reason be incapable of change or of relation to anything else.
The method is as distinctive as the conclusion. Nagarjuna does not usually assert a position and then defend it. He takes an opponent thesis, draws out what follows from it, and shows that the consequences contradict either the thesis itself or something else the opponent holds. The chapters proceed this way through motion, the self, fire and fuel, time, causation and nirvana. The technique is called prasanga, consequence, and it is the ground on which the school could claim to have no thesis of its own left standing to be refuted.
The doctrine of two truths keeps this from collapsing into nihilism. Conventionally things work, distinctions hold, and the path can be walked. Ultimately no analysis finds anything standing on its own. The two are not rival accounts of the world but two levels of description, and the tradition insists that the ultimate is reached through the conventional rather than by discarding it.