Paradigm Shift
<p >A <b>Paradigm shift</b> (or <b>revolutionary science</b>) is, according to <a href="http://en.wikipedia.org/wiki/Thomas_Samuel_Kuhn" title="Thomas Samuel Kuhn" class="mw-redirect" >Thomas Kuhn</a> in his influential book <i><a href="http://en.wikipedia.org/wiki/The_Structure_of_Scientific_Revolutions" title="The Structure of Scientific Revolutions" >The Structure of Scientific Revolutions</a></i>(1962), a change in the basic assumptions, or <a href="http://en.wikipedia.org/wiki/Paradigm" title="Paradigm" >paradigms</a>, within the ruling <a href="http://en.wikipedia.org/wiki/Theory" title="Theory" >theory</a> of <a href="http://en.wikipedia.org/wiki/Science" title="Science" >science</a>. It is in contrast to his idea of <i><a href="http://en.wikipedia.org/wiki/Normal_science" title="Normal science" >normal science</a></i>. According to Kuhn, "A <a href="http://en.wikipedia.org/wiki/Paradigm" title="Paradigm" >paradigm</a> is what members of a scientific community, and they alone, share." (The Essential Tension, 1977). Unlike a normal scientist, Kuhn held, "a student in the <a href="http://en.wikipedia.org/wiki/Humanities" title="Humanities" >humanities</a> has constantly before him a number of competing and incommensurable solutions to these problems, solutions that he must ultimately examine for himself." (<i>The Structure of Scientific Revolutions</i>).
Once a paradigm shift is complete, a scientist cannot, for example, reject the <a href="http://en.wikipedia.org/wiki/Germ_theory_of_disease" title="Germ theory of disease" >germ theory of disease</a> to posit the possibility that <a href="http://en.wikipedia.org/wiki/Miasma_theory_of_disease" title="Miasma theory of disease" class="mw-redirect" >miasma</a>causes disease or reject modern physics and optics to posit that <a href="http://en.wikipedia.org/wiki/Aether_(classical_element)" title="Aether (classical element)" >ether</a> carries light. In contrast, a critic in the Humanities can choose to adopt an array of stances (e.g., Marxist criticism, Freudian criticism, <a href="http://en.wikipedia.org/wiki/Deconstruction" title="Deconstruction" >Deconstruction</a>, 19th-century-style <a href="http://en.wikipedia.org/wiki/Literary_criticism" title="Literary criticism" >literary criticism</a>), which may be more or less fashionable during any given period but which are all regarded as legitimate. Since the 1960s, the term has also been used in numerous non-scientific contexts to describe a profound change in a fundamental model or perception of events, even though Kuhn himself restricted the use of the term to the hard sciences. Compare as a structured form of <i><a href="http://en.wikipedia.org/wiki/Zeitgeist" title="Zeitgeist" >Zeitgeist</a></i>.</p>