It is impossible to remember everything, so a process of winnowing must take place somehow.

ECONOMIST: Memory formation

It is impossible to secure everything.

WSJ: William Bratton: A Cop's-Eye View of Terrorism

Today it is impossible to be an expert about everything, yet the medical profession do not appear to have properly sub-divided their skills into contemporary areas of knowledge for the purposes of giving evidence in the courtroom.

BBC: Read your comments