Solving “Necessary Assumption” Questions

These questions ask you to find an assumption—an unstated premise—that the argument needs to be true:

• Which one of the following is an assumption on which the scientist’s argument depends?

• The conclusion relies on which one of the following assumptions?

• The argument presupposes which one of the following?

• The university president’s argument requires the assumption that…

• The conclusion does not follow unless…

Make a Few Strong Predictions 

While it might be hard to predict these answers word for word, you can often predict necessary steps that are missing from an argument before you read the question. Here’s how:

1. Find the main conclusion. If you’re having trouble, see LR: Closed Questions and study up on argument parts and indicators. 

2. Find the premises. Don’t assume that all statements other than the main conclusion are premises. They might include an opposing viewpoint, background information, or a concession. Stay focused on the evidence.

3. Figure out why the premises don’t prove the main conclusion. Even though you have accepted the premises as true, they still don’t prove the conclusion. Why not? What’s missing? 

Focus on exactly what the argument says. Don’t assume anything that isn’t explicitly stated.

Many arguments, by the way, have more than one problem. The more problems you notice, the better prepared you are to answer the question. After you spot one or two weaknesses, you’re ready to read the answers.

How to Evaluate Answer Choices

An argument can have many necessary assumptions. Even if you predict multiple necessary assumptions, you might not predict the correct answer. Making predictions remains a key step in engaging with the argument and ensuring that you understand its logic properly.

As you read each answer choice, the only question you need to ask yourself is: “Does this answer absolutely have to be true in order for the argument to work?” If the answer to that question is yes, then that answer choice is probably correct.

What to Look For

Look for an answer that you can safely say the author must agree with. In general, the weaker the answer, the better.

Be wary of answers that use all, any, each, every, only, most, and other strong words that restrict the words that follow them. (Don’t discount these words completely, though. Remember content is more important than word strength.)