What is called Nothingness is to be found only in time and in speech. In time it stands between the past and future and has no existence in the present; and thus in speech it is one of the things of which we say: They are not, or they are impossible.

The Notebooks of Leonardo da Vinci (Richter, 1888) - XIX Philosophical Maxims. Morals. Polemics and Speculations.