We must be careful, however, not to imagine that what Herakleitos thus discovered was a logical principle. This was the mistake of Lassalle’s book.[[373]] The identity in and through difference which he proclaimed was purely physical; logic did not yet exist, and as the principle of identity had not been formulated, it would have been impossible to protest against an abstract application of it. The identity which he explains as consisting in difference is simply that of the primary substance in all its manifestations. This identity had been realised already by the Milesians, but they had found a difficulty in the difference. Anaximander had treated the strife of opposites as an “injustice,” and what Herakleitos set himself to show was that, on the contrary, it was the highest justice (fr. [62]).
Fire.
69. All this made it necessary for him to seek out a new primary substance. He wanted not merely something out of which the diversified world we know might conceivably be made, or from which opposites could be “separated out,” but something which of its own nature would pass into everything else, while everything else would pass in turn into it. This he found in Fire, and it is easy to see why, if we consider the phenomenon of combustion, even as it appears to the plain man. The quantity of fire in a flame burning steadily appears to remain the same, the flame seems to be what we call a “thing.” And yet the substance of it is continually changing. It is always passing away in smoke, and its place is always being taken by fresh matter from the fuel that feeds it. This is just what we want. If we regard the world as an “ever-living fire” (fr. [20]), we can understand how it is always becoming all things, while all things are always returning to it.[[374]]
Flux.
70. This necessarily brings with it a certain way of looking at the change and movement of the world. Fire burns continuously and without interruption. It is therefore always consuming fuel and always liberating smoke. Everything is either mounting upwards to serve as fuel, or sinking downwards after having nourished the flame. It follows that the whole of reality is like an ever-flowing stream, and that nothing is ever at rest for a moment. The substance of the things we see is in constant change. Even as we look at them, some of the matter of which they are composed has already passed into something else, while fresh matter has come into them from another source. This theory is usually summed up, appropriately enough, in the phrase “All things are flowing” (πάντα ῥεῖ), though, as it happens, it cannot be proved that this is a quotation from Herakleitos. Plato, however, expresses the idea quite clearly. “Nothing ever is, everything is becoming”; “All things are in motion like streams”; “All things are passing, and nothing abides”; “Herakleitos says somewhere that all things pass and naught abides; and, comparing things to the current of a river, he says that you cannot step twice into the same stream” (cf. fr. [41])—these are the terms in which he describes the system. And Aristotle says the same thing, “All things are in motion,” “nothing steadfastly is.”[[375]] Herakleitos held, in fact, that any given thing, however stable in appearance, was merely a section in the stream, and that the matter composing it was never the same in any two consecutive moments of time. We shall see presently how he conceived this process to operate; meanwhile we remark that the idea was not altogether novel, and that it is hardly the central point in the system of Herakleitos. The Milesians held a similar view. The flux of Herakleitos was at most more unceasing and universal.
The Upward and Downward path.
71. Herakleitos appears to have worked out the details of the perpetual flux with reference to the theories of Anaximenes.[[376]] It is unlikely, however, that he explained the transformations of matter by means of rarefaction and condensation.[[377]] Theophrastos, it appears, suggested that he did; but he allowed it was by no means clear. The passage from Diogenes which we are about to quote has faithfully preserved this touch.[[378]] In the fragments, at any rate, we find nothing about rarefaction and condensation. The expression used is “exchange” (fr. [22]); and this is certainly a very good name for what happens when fire gives out smoke and takes in fuel instead.
It has been pointed out that, in default of Hippolytos, our best account of the Theophrastean doxography of Herakleitos is the fuller of the two accounts given in Laertios Diogenes. It is as follows:—
His opinions on particular points are these:—
He held that Fire was the element, and that all things were an exchange for fire, produced by condensation and rarefaction. But he explains nothing clearly. All things were produced in opposition, and all things were in flux like a river.