The name for an assumption made for the sake of contradiction What is the name (or adjective) for an assumption made for the sake of contradiction?
To be clear, I'm in search of an expression in the form "a(n) $\underline{\quad \quad \quad \quad}$ assumption".
Edit: Why are there votes to close this question? This question at least fits the tag "mathematical-writing" and is pertinent to the writing of mathematical research papers, no doubt.
 A: I liked the suggestion "the marked assumption", found in the comments. Unlike Willie Wong's suggestion the "contradictive assumption", the "marked assumption" only partially suggests the nature of the expression. This is hard to fix unless the expression is made standard.
An advantage of the "marked assumption" is that it can serve double-duty: Even in cases where the truth of the assumption is unknown, the expression is still relevant. This is particularly notable in the study of the Riemann Hypothesis where the Riemann Hypothesis is occasionally assumed and consequences derived therefrom. If the marked assumption holds, then all we have done is discover consistent structure. If the marked assumption fails, then our presumptive work can just be seen as a search for a contradiction.
A: Straw Man Proposal
A straw-man (or straw-dog) proposal is a brainstormed simple draft proposal intended to generate discussion of its disadvantages and to provoke the generation of new and better proposals.
https://en.wikipedia.org/wiki/Straw_man_proposal
A: Especially in the philosophy of religion, the term reductio premise is sometimes used.  A Google Scholar search for "reductio premise" (in quotation marks) turns up a few dozen references; one of the most highly cited is Robust vagueness and the forced-march sorites paradox, by Terence Horgan.
However, among mathematicians, I don't think there is any standard terminology.
A: Not the name, but a name: "contradictive assumption".
Google knows about 80 some odd uses of this in a mathematical context. I like it because the word "contradictive" has a dictionary definition that is more-or-less suited for the job, and the word immediately invokes the method of proof we are using.
