 Sometimes Gelug varies its ontological argument slightly, as does Tsongkhapa in the Lam gtso rnam gsum (The Three Principal Pathways), to stressing the unity of the two truths in terms of their causal efficiency. It argues that empty phenomena is causally efficient is crucial in understanding the inextricable relationship between ultimate truth and conventional truth. The argument takes two forms: (1) appearance avoids realism—the extreme of existence, and (2) emptiness avoids inhilism—the extreme of nonexistence. The former makes sense for Gelug because the appearance arises from causal conditions, and whatever arises from the causal conditions is a non-eternal or non-permanent. When the causal conditions changes any thing that dependently arises from them also changes. Thus the appearance avoids the realism. The latter makes sense because the empty phenomena arises from causal conditions, and whatever arise from the causal conditions is not a non-existent, even though it lacks intrinsic reality. Only when the causal conditions are satisfied do we see arising of the empty phenomena. Hence by understanding that the empty phenomenon itself is causally efficient, the bearer of cause and effect, one is not robbed by the extreme view of nihilism (1985: 252).