Suppressed correlative

Suppressed correlative or lost contrast is a semantic logical fallacy in which the arguer attempts to redefine two contrasting terms in such a way that one encompasses the other. As such, it is a form of straw man argument.

Form
Opponent: "All things are either X or not X." Response: "I define X in such a way that all things you say are not X are included in X."

Even if the definition used to redefine X is a more technically correct definition, it is still this fallacy, because it is still an attempt to avoid the opponent's actual argument which is based around two contrasting possibilities.

Examples

 * This is commonly used in debates about whether things are "art"; the question "is it art?" requires some possibility that something might not be art. The common response, that art is defined as an ineffable quality or a method of human expression, removes any possibility that something created by humans could not be classified as art, and therefore cannot possibly be addressing the opponent's actual argument.
 * Often used in attempts to classify science or atheism as religious beliefs; the substitute definition of "religion" will typically be so broad that almost any human association would qualify as a religion.
 * "I don't view humanity as the same species because we're not all the same" — Stefan Molyneux.