A History of Greek Philosophy / THE SCHOOL OF MILETUS / ANAXIMANDER
To modern criticism this may seem to be little better than verbiage, having, perhaps, some possibilities of poetic treatment, but certainly very unsatisfactory if regarded as science. But to this we have to reply that one is not called upon to regard it as science. Behind science, as much to-day when our knowledge of the details of phenomena is so enormously increased, as in the times when science had hardly begun, there lies a world of mystery which we cannot pierce, and yet which we are compelled to assume. No scientific treatise can begin without assuming Matter and Force as data, and however much we may have learned about the relations of forces and the affinities of things, Matter and Force as such remain very much the same dim infinities, that the originative ‘Infinite’ was to Anaximander.
It is to be noted, however, that while modern science assumes necessarily two correlative data or originative principles,—Force, namely, as well as Matter,—Anaximander seems to have been content with the formulation of but one; and perhaps it is just here that a kinship still remains between him and Thales and other philosophers of the school. He, no more than they, seems to have definitely raised the question, How are we to account for, or formulate, the principle of difference or change? What is it that causes things to come into being out of, or recalls them back from being into, the infinite void?
Cf. Anaximander Resources / Guthrie, The Early Presocratics and the Pythagoreans - A Synopsis of Greek Philosophy
Reference address : https://www.ellopos.net/elpenor/greek-texts/ancient-greece/history-of-philosophy/anaximander.asp?pg=3