Logos = the unifying formula or proportionate method of arrangement of things; a structural plan of things both individual and in sum.
In a technical sense: "measure," "reckoning," "proportion." The logos is not an "abstraction," but an actual constituent of things -- coextensive, in particular, with the primary cosmic constituent, fire.
H. seems to think that opposites are only apparent opposites -- e.g., fragments 202-205, pp. 189f.: any disunity is illusory -- they are in fact identical (e.g., the path up and down) or "process" into one another (e.g., living-dead; waking-sleeping, etc.)
[In my terms, H. stresses a logic of connection in the face of apparent differences, such that the differences stand -- and work together to form a complementary, complete whole. (CE)]
Again, the fragment quoted by Jones can be seen to mean not that the logos of things is neutral, amoral -- but that for god the separateness implied by opposites does not exist.
The constitution of things is compared to the back-stretched (hidden? tensional) connection in the bow and the lyre. This is the meaning of "strife between opposites" -- unity and balance depend on strife, the tensional, hidden connection between opposites.
The river illustrates the unity that depends on the preservation of measure and balance in change.
[It may also be noted that "river" refers to a unity that is not totally sensory, not totally spatially defined.]
Upon those that step into the same rivers different and different waters flow. It scatters and gathers, it comes together and flows away, approaches and departs.
Finally, in his cosmology (he has no cosmogony in the Milesian sense), Heraclitus shares the Milesian assumption that an analogy holds between the human and the natural -- especially in terms of human conceptions of justice:
The Sun will not overstep his measures, otherwise the Erinyes, ministers of Justice, will find him out.
[It may also be significant that the Erinyes are chthonic deities -- i.e., associated with an older goddess tradition which stresses precisely the logic of connection which we see run through Heraclitus.]
There is a new step here -- one characterized by K&R in terms of "an ethics which is for the first time formally interwoven with physics -- and, more broadly, a system in which all aspects of the world are explained in relation to a central discovery/insight, that natural changes are regular and balanced, and that the cause of this balance is fire/Logos."
That is to say, philosophy not only becomes still more comprehensive as it now encompasses an ethics which is rationally coherent with a physics: this means precisely that philosophy is both a means for understanding the world (physics -- what we'll later call theoria) and knowing how to live in the world (ethics -- what we'll later call praxis).
In still other terms, there appears here a new kind of wisdom:
If one does not expect the unexpected, one will not find it out, since it is not to be searched out, and difficult to compass.
"Only by understanding the central pattern of things can a man become wise and fully effective...."
Philosophy/science hence begins to move beyond the assumption that the world is intelligible to mind; it makes the additional claim that comprehending the world is necessary for wisdom and for being fully human -- and thus it is qualified to replace "religion" or mythopoetry as a guide to both the way things are and the way we are to behave in such a universe.