5 Steps to Solving Strengthen Logical Reasoning Questions

When you see a Strengthen question, find the argument's main flaw, an unstated assumption bridging the evidence and the conclusion, then look for the answer choice that patches it, often by ruling out an alternative explanation or shoring up the evidence. Strengthen is one of the most common Logical Reasoning question types, and Logical Reasoning makes up 2 of the LSAT's 3 scored sections.

What do you do when you see a Strengthen Logical Reasoning question?

Remember that Logical Reasoning is 2 of the 3 scored sections on the LSAT, and Strengthen questions show up often within it. Here’s a step-by-step guide to help you solve them.

1. Recognize that it’s a Strengthen question.

Some strengthen question stems:

“Which one of the following, if true, most strengthens the argument?”

“Which of the following, if true, would most justify the conclusion?”

2. Look for the main flaw (if present).

It will make some unwarranted (and unstated) assumption – the missing (and weakest) link between premises/evidence and conclusion.

3. Support the assumption and scan for answer choice that helps patch up the argument.

After you find the central flaw of the argument, fix it. Bridge the gap between evidence and conclusion. The correct answer may protect the argument against the flaw by:

denying an alternative possibility

promoting the evidence’s relevance to the conclusion

supporting the evidence’s validity (such as by saying a survey or study was properly conducted)

providing additional evidence to support the conclusion

4. Remember that the answer choices can contain information not mentioned in the stimulus.

Why? Because the question stem says “if true,” which allows the possibility of new information.

5. Remember that in “Strengthen EXCEPT” questions, 4 will strengthen the argument, and 1 will not.

The 1 that doesn’t strengthen will either weaken or have no effect. In logic, the opposite of strengthen is “not strengthen.”

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Contrast with Sufficient Assumption (aka Justify) question stems:

“Which one of the following, if true, allows the conclusion to be properly drawn?”

“The conclusion follows logically if which one of the following is assumed?”

Sufficient Assumption questions do strengthen the argument. In fact, they fully justify it by guaranteeing that the conclusion logically follows.

However, they should be approached differently than Strengthen questions. The major difference is that Sufficient Assumption (Justify) questions often reward a formal-logic approach, while Strengthen questions reward an informal-logic approach.

Frequently asked questions

How do you solve Strengthen questions on the LSAT?

Find the argument's central flaw, the unstated assumption linking evidence to conclusion, then look for the answer choice that patches it: by ruling out an alternative, supporting the evidence's validity, or adding evidence for the conclusion. Step 1 is finding the gap, which is why the list of LSAT flaws is the right thing to memorize first.

What's the difference between Strengthen and Sufficient Assumption questions?

Sufficient Assumption (Justify) answers guarantee the conclusion follows and reward a formal-logic approach. Strengthen answers only need to make the argument more likely true and reward an informal-logic approach; Sufficient Assumption answers always strengthen, but not every strengthener is sufficient.

Can a Strengthen answer choice include new information?

Yes. Because the question stem says "if true," the correct answer can introduce information that wasn't in the original stimulus, as long as it makes the argument more likely to be true. That's the reverse of Most Strongly Supported questions, where new information is a wrong answer.

How do Strengthen EXCEPT questions work?

4 of the 5 answer choices will strengthen the argument, and 1 won't; that 1 either weakens the argument or has no effect on it at all.

Watch a related lesson

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