It is from Heraclitus that Marcus derives one of his most
memorable motifs, that of the unstable flux of time and matter
in which we move. “We cannot step twice into the same
river,” Heraclitus had said, and we see Marcus expanding on
the observation: “Time is a river, a violent current of events,
glimpsed once and already carried past us, and another
follows and is gone” (4.43; and compare 2.17, 6.15).
Though Heraclitus was clearly the pre-Socratic who most
influenced Marcus, other thinkers leave traces as well.
Marcus twice borrows the poet Empedocles’ image of the
self-contained soul as a perfect sphere (8.41, 12.3), and he
alludes once to the mystic doctrines of the Pythagoreans
(11.27). Several entries explore the implications of phrases
attributed to Democritus, one of the inventors of the theory of
atoms, which would later inspire the Hellenistic philosopher
Epicurus.
Neither Heraclitus nor Socrates had founded a school.
That was an achievement reserved for Plato, and then for
Plato’s student Aristotle, who broke from his master to found
the Peripatetic movement. Marcus never refers to Aristotle,
though he does quote approvingly from the latter’s successor
Theophrastus (2.10). Probably more important was another
fourth-century B.C. movement: Cynicism. The Cynics, of
whom the first and most notorious was the irascible