Slide 13:

“No man ever steps in the same river twice, for it's not the same river and he's not the same man.”

― Heraclitus

Of course it’s not the same river — the river, is, what? The water flowing past your feet? The sound that it makes? These things are different at every moment. Our idea of ‘the river’ doesn’t correspond to anything in the real world. Understanding this concept means getting closer to an understanding of reality itself — once you fully absorb the impact of this idea, it changes you, from a person who didn’t have that understanding into one who does.

And as you bask in your newfound zen-like enlightenment, you discover an almost spiritually calming effect — the world as it is right now is the only thing that matters, not the state of the world as it was yesterday or as it will be tomorrow.

Slide 39:

“No man ever steps in the same river twice, for it's not the same river and he's not the same man.”

― Heraclitus

And I think Heraclitus probably understood it all along. There’s a paradox contained in this statement. If the concept of identity over time is meaningless, then what do we mean by ‘it’ and ‘he’?