Incalculably Diffusive Processes

A nice bit by Simon Blackburn:

Incalculably diffusive processes are real enough. Education is one of them. Sending a book or an idea into the marketplace may be the datable beginning of a diffusive process, but then there may be no datable end product. William Shakespeare's works diffuse after more than four centuries; Hume's after three. Their works are tributaries into the vast stream of thoughts and ideas and writings and political changes that made the modern world. But nobody can calculate the effect that just one work had, any more than they can calculate just how much of the growth of a flower, or how much of its beauty, was the result of any one raindrop falling on any one day. Yet nobody doubts that rain makes the garden grow. It is an incalculably diffusive process.