Can you step into the same river twice ?

“What did Heraclitus mean by saying that you cannot step into the same river twice. What were some of the opposing positions among the Pre-Socratics? Discuss this question in terms of the one and the many, or the temporal and the eternal.”


Heraclitus believed in what he referred to as “the unity of the opposites” and that everything was in a constant “flux” or a flowing change. The ideas of Heraclitus were related to his notion that fire was the essence that made up everything. Fire itself is in a constant state of change, burning its fuel and transforming what was into something other. This can also be seen as an example of the one and the many. Fire was related to the divine essence of existence. It encompassed all life and yet was part of the many things that make up life. Examples of the unity of the opposites, such as living-dead, hot-cold and wet-dry show how all existence is the same.
“Pairs of opposites exemplify the unity of all things by standing in several different relationships to each other. First, they may be logically indistinguishable, as in “Beginning and end are ‘common’ on the circle.” Second, they may be in unvarying mutual succession: thus, day and night are one, because, in modern terms, they are “temporally continuous”…Lastly, one opposite may be a necessary condition for the perception of another… (Edwards, p.478).”
For the different pairs, one of them changes consistently and exclusively into the other without there being a definitive ending only a change from one to the other. The meaning behind the words, you cannot step into the same river twice, is that the river itself is not the same once you have stepped out of it. The water that flows is what makes a river a river. Without the flowing change of water there would be no river. If the flow were to stop it would be a pond, therefore stepping into the river at one moment and then stepping into the same place at a different moment is not stepping into the same river only the same place. The river itself as since changed and is no longer the same as what it once was. Heraclitus used rivers in analogous ways to help show his ideas and by, “…Heraclitus comparing all things to a river, meant that they all changed all the time; applied to natural objects, this means that even apparently stable things are changing, although total balance is always maintained…(Edwards, p.479).”
In opposition to Heraclitus views on the unity of the opposites, Aristotle claims that Heraclitus is denying the law of non-contradiction. Aristotle’s Principle of Non-Contradiction (PNC) claims that humans could not understand the world around them if they were not bound by the principle of non-contradiction. Aristotle said, “It is impossible for the same thing to belong and not to belong at the same time to the same thing and in the same respect (http://plato.stanford.edu/entries/aristotle-noncontradiction/#1).”