585-528 BC Anaximenes
<p><b>Anaximenes of <a href="https://en.wikipedia.org/wiki/Miletus" title="Miletus">Miletus</a></b> (<a href="https://en.wikipedia.org/wiki/Help:IPA_for_English" title="Help:IPA for English">/ˌænækˈsɪməˌniːz/</a>; <a href="https://en.wikipedia.org/wiki/Greek_language" title="Greek language">Greek</a>: Ἀναξιμένης; c. 585 – c. 528 BCE) was an <a href="https://en.wikipedia.org/wiki/Ancient_Greece" title="Ancient Greece">Ancient Greek</a> <a href="https://en.wikipedia.org/wiki/Pre-Socratic" class="mw-redirect" title="Pre-Socratic">Pre-Socratic</a> <a href="https://en.wikipedia.org/wiki/Philosopher" title="Philosopher">philosopher</a> active in the latter half of the 6th century BC.<sup id="cite_ref-lindberg28_1-0" class="reference"><a href="https://en.wikipedia.org/wiki/Anaximenes_of_Miletus#cite_note-lindberg28-1">[1]</a></sup><sup id="cite_ref-graham_2-0" class="reference"><a href="https://en.wikipedia.org/wiki/Anaximenes_of_Miletus#cite_note-graham-2">[2]</a></sup> One of the three <a href="https://en.wikipedia.org/wiki/Milesian_School" class="mw-redirect" title="Milesian School">Milesian</a> philosophers, he is identified as a younger friend or student of <a href="https://en.wikipedia.org/wiki/Anaximander" title="Anaximander">Anaximander</a>.<sup id="cite_ref-3" class="reference"><a href="https://en.wikipedia.org/wiki/Anaximenes_of_Miletus#cite_note-3">[3]</a></sup><sup id="cite_ref-guthrie115_4-0" class="reference"><a href="https://en.wikipedia.org/wiki/Anaximenes_of_Miletus#cite_note-guthrie115-4">[4]</a></sup> Anaximenes, like others in his school of thought, practiced <a href="https://en.wikipedia.org/wiki/Material_monism" title="Material monism">material monism</a>.<sup id="cite_ref-lindberg29_5-0" class="reference"><a href="https://en.wikipedia.org/wiki/Anaximenes_of_Miletus#cite_note-lindberg29-5">[5]</a></sup><sup id="cite_ref-guthrie115_4-1" class="reference"><a href="https://en.wikipedia.org/wiki/Anaximenes_of_Miletus#cite_note-guthrie115-4">[4]</a></sup> This tendency to identify one specific underlying reality made up of a material thing is what Anaximenes is principally known for today.</p>
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While his predecessors <a href="https://en.wikipedia.org/wiki/Thales" title="Thales">Thales</a> and Anaximander proposed that the <i><a href="https://en.wikipedia.org/wiki/Arche" title="Arche">archai</a></i> (<a href="https://en.wikipedia.org/wiki/Grammatical_number" title="Grammatical number">singular</a>: <i>arche</i>, meaning the underlying material of the world) were water and the ambiguous substance <i><a href="https://en.wikipedia.org/wiki/Apeiron_%28cosmology%29" title="Apeiron (cosmology)">apeiron</a></i>, respectively, Anaximenes asserted that air was this primary substance of which all other things are made. The choice of air may seem arbitrary, but Anaximenes based his conclusion on naturally observable phenomena in the processes of <a href="https://en.wikipedia.org/wiki/Rarefaction" title="Rarefaction">rarefaction</a> and <a href="https://en.wikipedia.org/wiki/Condensation" title="Condensation">condensation</a>.<sup id="cite_ref-6" class="reference"><a href="https://en.wikipedia.org/wiki/Anaximenes_of_Miletus#cite_note-6">[6]</a></sup> When air condenses it becomes visible, as mist and then rain and other forms of precipitation. As the condensed air cools Anaximenes supposed that it went on to form earth and ultimately stones. In contrast, water evaporates into air, which ignites and produces flame when further rarefied.<sup id="cite_ref-guthrie124_7-0" class="reference"><a href="https://en.wikipedia.org/wiki/Anaximenes_of_Miletus#cite_note-guthrie124-7">[7]</a></sup> While other philosophers also recognized such transitions in states of matter, Anaximenes was the first to associate the quality pairs hot/dry and cold/wet with the density of a single material and add a quantitative dimension to the Milesian <a href="https://en.wikipedia.org/wiki/Material_monism" title="Material monism">monistic system</a>.<sup id="cite_ref-guthrie124_7-1" class="reference"><a href="https://en.wikipedia.org/wiki/Anaximenes_of_Miletus#cite_note-guthrie124-7">[7]</a></sup><sup id="cite_ref-8" class="reference"><a href="https://en.wikipedia.org/wiki/Anaximenes_of_Miletus#cite_note-8">[8]</a></sup></p>