Does the effect make its cause?
Cause and effect are mutually dependent like father and son. If there is no son there is no father, and if no father then no son. 

In this way Nagarjuna proves the non-existence of these things except as appearance/emptiness. 

He explains that the cause cannot exist prior to the effect, the effect cannot exist prior to the cause and they cannot come into existence simultaneously. Ergo, it's all smoke and mirrors.