“And so one ought to follow what is common. Although the principle is common, the majority of people live as though they had private understanding.” (here Waterfield 6; cp. DK B2, W 2, K 3)
“Thus it is necessary to follow the common (that is, the universal: for the ‘common’ is ‘universal’). But although the logos is common, most people live as though they possess a private purpose.” (Sweet 2)
It is often claimed that Heraclitus is the West’s first moral philosopher. Here the moral ought sounds proto-Kantian. Indeed, this seems to capture the essence of Kant’s view that we ought only act on a principle that we could will to be “universal law.”
But the principle here does not appear to apply only what Kant calls “practical reason,” but to apply to “theoretical reason” as well. It does not appear that Heraclitus separates the two: The logos permeates all of reality. The process of world unfolding is guided by rational principle. In all individual thinking and action one is also to be guided by an indivisible logos. In all such things, one should “follow the universal.”
In the passages preceding this one in Diels/Kranz and Waterfield editions, there is discussion of waking and sleeping. Those awakened are aware of a common world. We know the waking are in control of their lives. They direct their lives. Those who are asleep are guided by what we would now call unconscious forces. They are not free and consciously self-directed. We see here hints of a contrast between free and non-free action. On the one hand, there is self-aware action — as Heraclitus views it, guided by reason, the logos. On the other hand, there is the life of the sleeping, guided by private understanding — views that will not stand up to the test of rational examination. The former would appear to lead to freedom, or as Kant says, autonomy, since a life guided when awakened is surely freer than the non-self-directed life to which one is subjected when asleep.
Sweet’s translation, with a focus on purposes, brings a slightly different focus to light. In other passages (cp. F 1) Heraclitus suggests that we understand things in terms of their purposes (an idea that Aristotle later makes a bedrock of his substance metaphysics). We also understand ourselves in terms of our purposes. We weave our life narratives in reference to those things we live for and hold important. Here the point is that a life devoted to private purposes is the life of a sleeper — calling up zombie films, we might say, of the living dead. A life devoted to a common good is a life awake to truth. A rational, purposeful life requires a commitment to the good or to what is “common.”
Heraclitus is convinced most people do not follow such a principle but are guided by private understanding. However, despite his misanthropic tendencies, he here speaks of an ideal world as “necessary,” a world of individuals devoted to core goods of a common life, guided by a principle that is rational and theoretically able to be affirmed by all.