Assumption Questions In Critical Reasoning

by on September 24th, 2009

For many students, Assumption questions are the most difficult type of Critical Reasoning problem. An assumption is simply an unstated premise of the argument; that is, an integral component of the argument that the author takes for granted and leaves unsaid. In our daily lives we make thousands of assumptions, but they make sense because they have context and we have experience with the way the world works.

Think for a moment about the many assumptions required during the simple act of ordering a meal at a restaurant. You assume that: the prices on the menu are correct; the items on the menu are available; the description of the food is reasonably accurate; the waiter will understand what you say when you order; the food will not sicken or kill you; the restaurant will accept your payment, et cetera. In an GMAT question, you are faced with the difficult task of figuring out the author’s mindset and determining what assumption he or she made when formulating the argument. This task is unlike any other on the GMAT.

Because an assumption is an integral component of the author’s argument, a piece that must be true in order for the conclusion to be true, assumptions are necessary for the conclusion. Hence, the answer you select as correct must contain a statement that the author relies upon and is fully committed to in the argument. Think of an assumption as the foundation of the argument, a statement that the premises and conclusion rest upon. If an answer choice contains a statement that the author might only think could be true, or if the statement contains additional information that the author is not committed to, then the answer is incorrect. In many respects, an assumption can be considered a minimalist answer. Because the statement must be something the author believed when forming the argument, assumption answer choices cannot contain extraneous information. For example, let us say that an argument requires the assumption “all dogs are intelligent.” The correct answer could be that statement, or even a subset statement such as “all black dogs are intelligent” or “all large dogs  are intelligent” (black dogs and large dogs being subsets of the overall group of dogs, of course). But, additional information would rule out the answer, as in the following case: “All dogs and cats are intelligent.” The additional information about cats is not part of the author’s assumption, and would make the answer choice incorrect.

Because assumptions are described as what must be true in order for the conclusion to be true, some students ask about the difference between Must Be True question answers and Assumption question answers. The difference is one that can be described as before versus after: Assumption answers contain statements that were used to make the conclusion; Must Be True answers contain statements that follow from the argument made in the stimulus. In both cases, however, there is a stringent requirement that must be met: Must Be True answers must be proven by the information in the stimulus; Assumption answers contain statements the author must believe in order for the conclusion to be valid.

Question stem examples:

“The argument in the passage depends on which of the following assumptions?”

“The argument above assumes that”

“The conclusion above is based on which of the following assumptions?”

“Which of the following is an assumption made in drawing the conclusion above?”

“The conclusion of the argument above cannot be true unless which of the following is true”

1 comment

  • Could you recommend something good to read on the subject of questioning assumptions, or critical  thinking, that has good examples, like your restaurant example, and exercises to illuminate this practice.  I would be very grateful if you could get back to me.
    Many thanks,

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