An assumption is a statement or idea that you accept as true without proof or demonstration. Suppose, for instance, that a student is writing a politics paper that argues against NATO involvement in the Bosnian conflict. The author may believe that, given the long history of ethnic and political fighting in this region of the former Yugoslavia, any peace settlement is doomed to failure. But readers may not agree, and they may not be able to follow an argument that simply takes as a given that peace in Bosnia is impossible. In addition, if the author's supposition is left unexplored, any argument he presents against NATO intervention will be incomplete.
Unstated assumptions can also lead to the serious logical error of non sequiturs .
Suppose the author of the paper on Bosnia writes that there is a long history of war in Bosnia and provides pages of historical evidence to show that this is true. Even if he demonstrates that there has been a pattern of conflict in the region, the author's conclusion that all future efforts at peace will fail does not necessarily follow. If a writer who holds such an opinion explores why he thinks peace will necessarily fail in Bosnia, he may discover that stereotypes are at the root of his claim, and that his ideas are therefore invalid. Even if you are careful to avoid unfounded suppositions in your own work, you may face the delicate task of writing about an author who makes false assumptions or holds certain prejudices. When you discuss this writer's ideas, always make clear that these attitudes are hers, not your own.