Sufficient Assumption Questions
Key Takeaways
- A sufficient assumption, when added to the premises, must guarantee the conclusion rather than merely improve the argument.
- The fastest route is usually to find new language in the conclusion and bridge it back to the premises.
- Strong answer language can be correct on sufficient-assumption questions because the task is proof, not modest support.
- Conditional and principle-based sufficient-assumption items require exact direction, not just a related idea.
The Proof Standard
A sufficient assumption is enough to make the conclusion follow. It may be stronger than what the author strictly needs. That is the key difference from necessary assumption: sufficient means enough; necessary means required. On this task, a helpful answer can still be wrong if the conclusion remains unproved.
LSAT Logical Reasoning regularly uses short arguments where the author jumps from one phrase to another. Sufficient-assumption stems ask you to add the missing plank. Treat the stem as a proof instruction: premises plus answer must force the conclusion.
Stem Signals
| Stem wording | Translation |
|---|---|
| conclusion follows logically if | add a statement that proves it |
| properly drawn if assumed | make the inference valid |
| enables the conclusion to be drawn | bridge all remaining gaps |
| if true, allows the conclusion | supply sufficient support |
Do not use the strengthen standard here. A choice that makes the conclusion more plausible is not enough. Ask whether the author could put the choice into the stimulus and then validly say therefore.
Match New Terms
Most sufficient-assumption answers are built from new terms. Compare the premise language to the conclusion language. If the premise says a clinic verified all dosages and the conclusion says the clinic met the safety standard, the answer probably connects verified dosages to meeting the safety standard.
The bridge often runs from premise term to conclusion term. If the answer reverses the direction, it may sound right while doing nothing. Verified dosages -> safety standard is useful. Safety standard -> verified dosages does not prove the clinic met the standard just because dosages were verified.
Bridge Checklist
- What exact claim is the conclusion making?
- Which word or standard appears only in the conclusion?
- Which premise term is closest to that new language?
- Would the answer connect premise term to conclusion term in the right direction?
- After adding the answer, is any gap still open?
If a gap remains, keep looking. A sufficient assumption should leave no real daylight between evidence and conclusion.
Conditional Items
Sufficient-assumption questions often test conditional chains. Suppose the premises give A -> B and the conclusion requires A -> C. A sufficient answer may be B -> C. The answer does not have to repeat A. It can complete the chain.
Direction is everything. If the answer says C -> B, it gives a necessary condition for C, not a route to C. Many wrong answers reverse the missing link because the same words appear. Translate before you trust the match.
A compact notation method helps:
| Given | Goal | Useful bridge |
|---|---|---|
| certified -> trained | certified -> eligible | trained -> eligible |
| published -> reviewed | published -> credible | reviewed -> credible |
| violates rule -> sanction | violates rule -> appeal denied | sanction -> appeal denied |
This table is not a formula for every item. It is a reminder that the answer must connect the chain in a direction that reaches the conclusion.
Principle Bridges
Some sufficient-assumption questions are principle questions in disguise. The stimulus gives facts and a recommendation, but the missing rule is normative. If the premise says a policy protects confidential medical information and the conclusion says the policy should be adopted, the sufficient answer may state that any policy protecting such information should be adopted.
That answer may feel too strong. On sufficient-assumption questions, strong rules are allowed if they prove the conclusion. The danger is not strength by itself. The danger is strength aimed at the wrong target.
Wrong Answer Patterns
The most common wrong answer is a partial bridge. It links one premise to the conclusion but leaves another condition unresolved. Another common wrong answer strengthens a premise rather than proving the conclusion. A third reverses necessary and sufficient conditions.
Also watch answers that prove a nearby conclusion. If the author concludes that a regulation must be rejected, an answer proving that the regulation is expensive is not sufficient unless another premise or the answer itself establishes that expensive regulations must be rejected.
Add-And-Test Method
For each finalist, insert the answer after the premises and read the conclusion. The question is not whether the answer sounds relevant. The question is whether the argument is now valid or at least conclusively supported under the stem's standard.
If two answers seem strong, prefer the one that uses the exact conclusion language. LSAT sufficient-assumption answers often mirror the conclusion because they are designed to close the last link. A choice that discusses a broader policy concern may be attractive but unneeded.
Timing And Review
These questions can be fast when the gap is a clean term bridge. They can be slow when answer choices are long conditional rules. If the stem signals sufficiency, do not over-read the stimulus for every possible weakness. Find the conclusion, mark new language, and search for a proof bridge.
In review, write the finished proof. Premise one, premise two, added assumption, therefore conclusion. If you cannot explain why the conclusion now follows, you may have selected a strengthener rather than a sufficient assumption.
The exam skill is exactness. On a current LSAT with two scored LR sections, sufficient-assumption questions reward students who can move from ordinary-language argument to proof structure without making the answer stronger, weaker, or reversed in the wrong place.
City analyst: Any city contract that substantially increases long-term maintenance costs should be rejected. The proposed ferry terminal contract would require hiring a new maintenance crew for the next 15 years. Therefore, the proposed ferry terminal contract should be rejected. Which assumption, if true, allows the conclusion to follow?