Psyche
<p >The <b>soul</b> – in many traditional <a href="http://en.wikipedia.org/wiki/Spirituality" title="Spirituality" >spiritual</a>, philosophical, and <a href="http://en.wikipedia.org/wiki/Psychology" title="Psychology" >psychological</a> traditions – is the <a href="http://en.wikipedia.org/wiki/Incorporeality" title="Incorporeality" >incorporeal</a> and <a href="http://en.wikipedia.org/wiki/Immortality_of_the_Soul" title="Immortality of the Soul" class="mw-redirect" >immortal</a> essence of a person, living thing, or object.<sup id="cite_ref-0" class="reference" ><a href="http://en.wikipedia.org/wiki/Soul#cite_note-0" >[1]</a></sup> Some religions teach that all biological organisms have souls, and others further still that even non-biological entities (such as rivers and mountains) possess souls. This latter belief is called <a href="http://en.wikipedia.org/wiki/Animism" title="Animism" >animism</a>.<sup id="cite_ref-1" class="reference" ><a href="http://en.wikipedia.org/wiki/Soul#cite_note-1" >[2]</a></sup> <a href="http://en.wikipedia.org/wiki/Anima_mundi" title="Anima mundi" >Anima mundi</a> and the Dharmic <a href="http://en.wikipedia.org/wiki/Atman_(disambiguation)" title="Atman (disambiguation)" class="mw-redirect" >Ātman</a> are concepts of a "world soul." Some religious thinkers, such as <a href="http://en.wikipedia.org/wiki/Thomas_Aquinas" title="Thomas Aquinas" >Thomas Aquinas</a>, attribute souls to all organisms but teach that only human souls are immortal.<sup id="cite_ref-2" class="reference" ><a href="http://en.wikipedia.org/wiki/Soul#cite_note-2" >[3]</a></sup>
<i>Soul</i> can function as a synonym for <i><a href="http://en.wikipedia.org/wiki/Spirit" title="Spirit" >spirit</a></i>, <i><a href="http://en.wikipedia.org/wiki/Mind" title="Mind" >mind</a></i> or <i><a href="http://en.wikipedia.org/wiki/Self_(spirituality)" title="Self (spirituality)" class="mw-redirect" >self</a></i>;<sup id="cite_ref-3" class="reference" ><a href="http://en.wikipedia.org/wiki/Soul#cite_note-3" >[4]</a></sup> scientific works, in particular, often consider 'soul' as a synonym for 'mind'<sup class="Template-Fact" >[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed" >citation needed</a></i>]</sup>.</p>
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<a href="http://en.wikipedia.org/wiki/Aristotle" title="Aristotle" >Aristotle</a> defined the soul or <i>psyche</i> (ψυχή) as the <i><a href="http://en.wikipedia.org/wiki/First_actuality" title="First actuality" class="mw-redirect" >first actuality</a></i> of a naturally organized body,<sup id="cite_ref-10" class="reference" ><a href="http://en.wikipedia.org/wiki/Soul#cite_note-10" >[11]</a></sup> but argued against its having a separate existence from the physical body. In Aristotle's view, the primary activity of a living thing constitutes its soul; for example, the soul of an eye, if it were an independent organism, would be seeing (its purpose or <a href="http://en.wikipedia.org/wiki/Final_cause" title="Final cause" class="mw-redirect" >final cause</a>).
The various <a href="http://en.wikipedia.org/wiki/Faculties_of_the_soul" title="Faculties of the soul" >faculties of the soul</a> or psyche, such as nutrition, sensation, movement, and so forth, when exercised, constitute the "second" actuality, or fulfillment, of the capacity to be alive. A good example is someone who falls asleep, as opposed to someone who falls dead; the former actuality <i>can</i> wake up and go about their life, while the second actuality can no longer do so. Aristotle identified three hierarchical levels of living things: plants, animals, and people, for which groups he identified three corresponding levels of soul, or biological activity: the nutritive activity of growth, sustenance and reproduction which all life shares; the self-willed motive activity and sensory faculties, which only animals and people have in common; and finally <i>reason,</i> of which people alone are capable. Aristotle treats of the soul in his work, <i><a href="http://en.wikipedia.org/wiki/On_the_Soul" title="On the Soul" >De Anima</a></i> (<i>On the Soul</i>). Aristotle concludes, in the fifth chapter of the third book of this work, that the human active intellect is immortal.<sup id="cite_ref-11" class="reference" ><a href="http://en.wikipedia.org/wiki/Soul#cite_note-11" >[12]</a></sup></p>