Solving “Sufficient Assumption” Questions

These open questions ask you to find an assumption (a missing premise) that, if it were true, would 100% prove the main conclusion:

• Which one of the following, if assumed, would justify the conclusion? 

• Which one of the following, if assumed, enables the argument’s conclusion to be properly drawn?

• The argument’s conclusion can be properly inferred if which one of the following is true?

• The speaker’s main conclusion logically follows if which one of the following is assumed?

Make a Strong Prediction 

A sufficient assumption is a new fact that, in tandem with the premises, proves the conclusion. After you add it to the argument, you don’t need to add anything else. So ask yourself: “What would I add to this argument to fix its problems and prove the conclusion?”

There’s often only one flaw, but if there are multiple issues, the correct answer must fix all of them.

If you notice anything in the conclusion that is not mentioned in the premises, then that idea must be addressed by the correct answer.

To make a strong prediction, start by understanding the argument inside and out. Find the main conclusion and the premises (review here), figure out why the premises don’t prove the main conclusion, then figure out what would prove the main conclusion. If the argument has a gaping hole, patch it up.

Your job is to be the emergency first-responder who’s been dispatched to save the argument. 

What to Look For

As you read each answer choice, ask yourself:

1. Does this answer prove the main conclusion?‍

2. Does this answer completely fix every problem with the argument? 

Remember, take all five answer choices as true. The correct answer will give you new evidence that proves the main conclusion by fixing all its flaws.

Because we’re trying to prove the conclusion beyond a shadow of a doubt, stronger language is usually better. Be wary of answer choices that say “some” or “many,” as those words are often not sufficient to prove the conclusion. However, content is much more important than word strength, so focus on understanding the argument.