Necessary assumptions | Quick guide

A quick guide to approaching questions that ask you to find an assumption required by the argument

This question asks you to identify the claim that must be true or is required in order for the argument to work. In other words, there is a silent, unspoken piece of support that the arguer is taking for granted to be true, and your job is to explicitly identify what that piece is. A good way to think of necessary assumptions is: if that statement were to be false, the argument’s reasoning would be undermined.

Example: Water is necessary to survival.

How do we know? Because if we took water away, we wouldn’t survive. The same is true for an assumption that’s necessary to an argument.

Common wrong choice types

Too strong: When a choice is too strong, you’ll want to ask yourself, “Does this statement really have to be true, to the degree that’s expressed here, in order for the argument to hold? Or would a lesser version of this statement still work?”
Irrelevant: When a choice is irrelevant to the argument, you’ll want to ask yourself, “Does this even matter to the argument, or is it just something that’s ‘nice to know’ or ‘confusing because it’s irrelevant’?”
Detrimental: Ask yourself, “Does the argument actually depend on this statement, or is it actually worse off in light of this statement?”

It’s best to make a prediction after you analyze the stimulus, since it’s easy to get lost in the choices otherwise. You won’t always be able to, but it’s a good idea to practice predicting until it becomes easier.

Some helpful practices

✓ Identify the conclusion and support. Make sure to separate the conclusion from the support—this will make the gap in the argument more visible to you. It can also be helpful to phrase the argument’s structure to yourself as, “The arguer believes [conclusion], because [support]” in order to detect any leaps in logic or scope.

✓ Find a gap, if there is one. Is there a gap in scope between the support and the conclusion? Does the topic shift in a meaningful way? If so, then that gap needs to be connected by the assumption.

✓ Find an overlooked possibility, if there is one. Is there something that the arguer might be missing? Some kind of possibility that’s not been accounted for? If so, then that possibility must be accounted for by the assumption.

✓ Match a choice to your prediction. If you’ve predicted one possible necessary assumption, find the choice that matches your prediction. Be careful not to get distracted along the way. Note that it's sometimes more challenging to identify a prediction for a necessary assumption than it is for other question types, so don't feel discouraged if you can't find a prediction.

✓ Eliminate strategically. If you weren’t able to make a prediction, look to eliminate choices by testing them against your knowledge of common wrong choices—are the strongly-worded choices too strongly-worded? Which choices aren’t even relevant to the argument?

✓ Negate. If needed, test choices by negating them. If negating the truth of a choice causes the argument to be undermined, then that’s the answer. If negating the truth of a choice causes the argument to be strengthened or be unaffected, then that choice is incorrect.

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