The Greek philosopher Heraclitus is regarded as one of the distant godfathers of rheology, and it is a requirement that his name and motto "Everything Flows" appears in every rheology book. (I plead guilty, as the motto appeared in my graduate thesis.)
Heraclitus lived in Ephesus around 500 BC, and developed a doctrine that stated that everything is in a state of flux. His most famous statement, as quoted by Plato, is that "[you] cannot step twice into the same river; for fresh waters are ever flowing in upon you."
Interestingly, as I was researching Heraclitus, I found that Bertrand Russell suggested the "everything flows" statement was apocryphal. In addition, Heraclitus's Wikipedia page attributes the phrase to the 6th century pagan philosopher Simplicius of Cilia.
Source: A History of Western Philosophy by Bertrand Russell