E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Ex nihilo nihil fit. From nothing comes nothingi.e. every effect must have a cause. It was the dictum of Xenophans, founder of the Eleatic school (sixth century), to prove the eternity of matter. We now apply the phrase as equivalent to You cannot get blood from a stone. You cannot expect clever work from one who has no brains.