Editing Theory (section)

===Intertheoretic reduction and elimination===
{{Main|Intertheoretic reduction}}
If a new theory better explains and predicts a phenomenon than an old theory (i.e., it has more [[explanatory power]]), we are [[Theory of justification|justified]] in believing that the newer theory describes reality more correctly. This is called an ''intertheoretic reduction'' because the terms of the old theory can be reduced to the terms of the new one. For instance, our historical understanding about ''sound'', ''light'' and ''heat'' have been reduced to ''wave compressions and rarefactions'', ''electromagnetic waves'', and ''molecular kinetic energy'', respectively. These terms, which are identified with each other, are called ''intertheoretic identities.'' When an old and new theory are parallel in this way, we can conclude that the new one describes the same reality, only more completely.

When a new theory uses new terms that do not reduce to terms of an older theory, but rather replace them because they misrepresent reality, it is called an ''intertheoretic elimination.'' For instance, the [[superseded scientific theories|obsolete scientific theory]] that put forward an understanding of heat transfer in terms of the movement of [[caloric fluid]] was eliminated when a theory of heat as energy replaced it. Also, the theory that [[phlogiston]] is a substance released from burning and rusting material was eliminated with the new understanding of the reactivity of oxygen.