원성실성은 원만, 구경 (究竟), 진실의 의미로서 불성, 법성, 진여, 법신 등을 구족한 자성 (自性)을 말함. 원성실성이란 또 의타기성 (依他起性)에서 분별심을 일으키지 않으면 원성실성이고, 분별을 일으키면 변계소집( 遍計所執)이 됨을 뜻하기도 함

The complete and perfect real nature or reality: The ultimate emptiness of the imagined and relative truths. It is also the alternate name for Buddha-nature, Dharma-nature, the true-suchness, etc.
In other words, if you do not arouse a discriminating mind with an interdependent nature of things, that is what absolute true-nature is. That means we should never arouse the mind to discriminating things, which is called manipulation of the mind or mental construction and attachment.