Nihilism is the philosophical posture that denies the existence of everyone and everything. Eternalism imputes permanent existence to that which is temporary. The former deprecates, the latter exaggerates.
Both, sooner or later, lead to antinomian behaviors. Everything is the same to nihilists and eternalists, either because all is nothing, or because all is indistinctly ‘divine’.
Those who cultivate the Dharma perceive all that exists as existing, and all that does not exist as not existing, without deprecation or exaggeration. The higher the view, the more careful their conduct.