Final answer:
Gaining supernatural certainty of the external world's reality would challenge ontological nihilism, which is often grounded in solipsism. Such certainty undermines the nihilistic view that nothing exists outside the mind, reaffirming the significance of cosmological and ontological discussions in the philosophy of reality.
Step-by-step explanation:
If one were to attain a supernatural certainty that the external world is factually real, it would indeed pose a significant challenge to arguments for ontological nihilism, which posits that nothing is real. The notion of 'nothingness' often relies on some form of solipsistic framework, wherein the only certainty is that one's own mind exists. However, with a confirmed external reality, the ground for ontological nihilism becomes unstable.
The Western tradition has generally operated under the assumption that 'nothing can come from nothing,' often leading to the cosmological argument for God's existence. However, this argument is not definitive proof, as it doesn't provide sufficient reasoning to disprove the existence of alternative explanations for the universe.
The reality of the mind and external world have been longstanding philosophical debates. It's crucial to distinguish between what exists intra-mentally (within the mind) and extra-mentally (outside the mind). While cosmological arguments from experience attempt to deduce the existence of God by observing effects and postulating a cause, ontological arguments use reason a priori to establish God's existence.
Thus, a supernatural certainty about the reality of the external world would not only dispute ontological nihilism but also influence discussions around solipsism, the cosmological argument, and the nature of truth.