How things appear and how they actually exist differ greatly. A person engaging in practice of the perfection of wisdom does this kind of analysis and then examines how things appear in ordinary experience, alternating analysis and comparison with the usual mode of appearance in order to notice the discrepancy between the actual mode of subsistence of phenomena and their appearance.
In this way the inherent existence which is the object of negation will become clearer and clearer. As much as the object of negation becomes clearer, so much deeper will your understanding of emptiness become. Finally, you will ascertain a mere vacuity that is a negative of inherent existence.
From Kindness, Clarity, and Insight, page 53