[coldtea]

>Technically you can. You just have to flow back down a different one to the source again

It wont be the same, as all arrangements of molecules would have changed, not to mention be entirely different water molecules.

Which was Heraclitus point (metaphorically): the things we wish to do again ("twice"), we'll always have to do them in a changed environment.

[loa_in_]

So it is when you blink while swimming in one stream