Thinking mind makes asertions, contradictions "it is, it is not". ordinary thinking conceptual is temporary, it is not existing other than by invented apprehension.
Wisdom (purity...) is timeless, empty, no base. In thought is no timeless.
"Despite the fact that we are a ceaselessly transforming stream, interdependent with other beings and the whole world, we imagine that there exists in us an unchanging entity that characterizes us and that we must protect and please. A thorough analysis of this reveals that it is only a fictitious mental construct".
Shechen Rabjam Rinpoche.