Like Thales, Anaximander was a monist. But he rejected Thales' supposition that water is the material archÃÂª. Instead, he proposed the apeiron (the indefinite, or the infinite). Why did he do this?
There is only one extant fragment (6 = B1). It was recorded by the commentator Simplicius (6th C.), who was preserving an account of Anaximander given by Aristotle's student Theophrastus; it's possible that Simplicius may have gotten the quote from yet another commentator, Alexander, in his now lost commentary on Aristotle's Physics. Here is the fragment:
They pay penalty and retribution to each other for their injustice in accordance with the ordering of time.
Before trying to figure out what this means, let's look at the context in Simplicius:
Anaximander ... said that the indefinite was the first principle and element of things that are, and he was the first to introduce this name for the first principle [i.e.,
he was the first to call the first principle indefinite]. He says that the first principle is neither water nor any other of the things called elements, but some other nature which is indefinite ....
Here's a quite different translation (Barnes, EGP 74-75):
Anaximander ... said that the infinite is principle and element of the things that exist. He was the first to introduce this word "principle". He says that it is neither water nor any other of the so-called elements but some different infinite nature ....
There are two significant differences between these translations:
1. The text (which reads, literally: he was the first to use this name of [the] principle) is ambiguous as to which word (archÃÂª, 'principle' or apeiron, 'infinite', 'indefinite') Anaximander introduced. This is not so important.
2. Should we translate apeiron as "infinite" or "indefinite"? This is important, and we will have to...