LSAT Inference questions: what must be true, not what sounds true

An Inference question gives you a set of statements and asks what must be true if they are. Stems read "if the statements above are true, which one of the following must also be true?" or "the statements above, if true, most strongly support which one of the following?" The passage is usually not an argument at all — just facts, laid out.

The job is narrow and the discipline is unusual: you are not reasoning toward the best explanation, not judging what is likely, and not applying anything you know about the topic. You are asking whether each answer is guaranteed by the words on the page.

Inference and Assumption point in opposite directions

These two get confused constantly, and the confusion is worth clearing once. An Assumption question asks what the argument needed on the way in — an unstated premise. An Inference question asks what comes out — a conclusion the statements force. In goes assumption, out comes inference. Students who miss both types usually have not separated them, and the fix is a single question at the stem: is this asking what the author must have believed, or what I must now believe?

Why the timid answer usually wins

Written for this page: every violinist in the orchestra also plays piano. Some pianists in the city have never performed publicly. Nobody who has never performed publicly is a member of the orchestra.

What follows? That every violinist in the orchestra has performed publicly — they play piano, they are orchestra members, and no orchestra member is among those who have never performed. What does not follow is anything about pianists in the city generally, or about whether the orchestra has violinists at all. The statements never said it does.

That is the characteristic shape of the type. The credited answer often sounds underwhelming — hedged, partial, obviously true once stated. The wrong answers sound like real conclusions someone might draw. The test is exploiting the ordinary human habit of filling in what a passage implies socially rather than what it entails logically.

The words that decide these questions

• Some means at least one — possibly all. An answer that turns "some" into "many" or "most" has added information.
• Most means more than half — it does not mean nearly all, and two "most" statements about the same group do overlap, which is occasionally the point.
• All and only are not interchangeable. "All A are B" says nothing whatsoever about whether B are A.
• Not all is not the same as none. This one shows up in wrong answers constantly.
• May, might, and could in an answer make it far easier to guarantee — which is why hedged answers are so often correct here, and so often wrong on Assumption questions.

A practical filter: before selecting, try to find a way the answer could be false while every statement stays true. If you can construct one, it is not the answer. On the harder items this is faster than re-reading, because the counterexample either appears in a few seconds or does not exist.