The Ionian school, a type of Greek philosophy centred in Miletus, Ionia, in the 6th and 5th centuries BC, is something of a misnomer. Although Ionia was a center of Western philosophy, the scholars it produced, including Thales, Anaximander, Anaximenes, Heraclitus, Anaxagoras, Archelaus, and Diogenes of Apollonia, had such diverse viewpoints that they cannot all be thought of as having belonged to one particular school of philosophy. Aristotle called them physiologoi, meaning 'those who discoursed on nature', but did not group them together as an "Ionian school". The classification can be traced to the second-century historian of philosophy Sotion. They are sometimes referred to as cosmologists, since they were largely physicalists who tried to explain the nature of matter.