Before the invention of writing the range of one man’s influence over
another was limited to the range of sight, sound and scent; besides this
there was trail, of many kinds. Trail unintentionally left is, as it
were, hidden sight. Left intentionally, it is the unit of literature.
It is the first mode of writing, from which grew that power of extending
men’s influence over one another by the help of written symbols of all
kinds without which the development of modern civilisation would have
been impossible.