Kenji Tomiki used to say "mushin mugamae".
It is from the "emptines" the technique is created, without the emptines, the opponent will always read your intention to apply a technique.
Basically we attach to the opponents power, expressed by his body, we don't pull or push, we align our body and apply power. When we apply power, we use the polarity between both hands (active and passive hand changing constantly as complimentary forces).
From the emptines (mu) comes the power which creates a waza with the intention to throw (nage waza or atemi waza) or to control (katame waza and kansetsu waza).
what do you mean by "emptiness"? is it a state of mind or body or both? the chinese called it wuji, and i sure hope they don't mean it a "blond" moment.