Who said, "One cannot step twice in the same river"?

We know from history that Heraclitus somewhere said that all things are in process and nothing stays still and likening existing things to the stream of a river he said, "One cannot step twice into the same river". All things flow, nothing abides. We cannot step into the same river twice, for waters in rivers, lakes, and streams are continually flowing.

Everything in the universe is in constant movement. This expression by Heraclitus is only a metaphor. It means that people really can't go back in time not even for a minute. The Earth, air, water, wind, planets, and everything in the universe especially human beings are changing all the time. One moment or situation in time is not the same moment or situation ever again and therefore every moment is unique.

Heraclitus was born c. 540 BC in Ephesus, Anatolia. He died in c. 480 BC. He was a Greek philosopher who is best remembered for his cosmology, in which fire forms the basic material principle of an orderly universe. Little is known about his life, and the one book that he apparently wrote has been lost. Scholars however have found several writings by Heraclitus. He is said to have specifically wrote, "The world order is an ever-living fire kindling in measures and being extinguished in measures.”