Logical Reasoning makes up two of the three scored sections on the LSAT, and about two-thirds of all the questions that count toward your score. So it is worth knowing what it can actually ask you.
Most guides answer that with an alphabetical list of a dozen or so type names. LSAC never publishes an official list, every prep company draws the lines somewhere slightly different, and we track nineteen. They're below, with worked examples.
But a word first about what a list like this is for, because it is easy to use it in a way that will cap your score.
One argument, five different questions
The types are not nineteen separate skills. Most of them are different demands made on the same underlying reading.
Take a simple argument: a study found that houses with professionally landscaped front yards sold for about 10 percent more than houses without, so adding landscaping will increase a house's sale price. The weak point is the same no matter what gets asked. The evidence shows only that landscaping and higher prices went together, while the conclusion claims one produces the other, which treats the two groups of houses as though nothing else about them differed.
Now watch how the question changes the job and nothing else:
- Flaw: name it. The argument treats evidence of a correlation as though it established causation.
- Weaken: make it worse. Those houses were also in more desirable neighborhoods.
- Strengthen: shore it up. The two groups of houses were comparable in location, size, and condition.
- Necessary Assumption: state what the argument needed. Nothing other than the landscaping accounts for the price difference.
- Evaluate: ask what would settle it. Whether the landscaped houses differed from the others in some further way that affects price.
One piece of reading, five questions answered, and notice that the reading came first. You do not need to know which of the five you're facing in order to do it. That full walkthrough is in analyze, predict, eliminate.
This is why the list below is a reference and not a procedure. If you learn these types as nineteen recipes, as in see this stem, do this thing, you will do fine on the questions that look like the ones you studied, and you will stall on the ones that don't, which are precisely the questions standing between you and a higher score. The students who keep improving are the ones who got good at reacting to a stimulus they've never seen.
What a stimulus can be
Before any of this becomes about types, there are three things a stimulus can be, and each one asks for a different reaction:
- An argument that doesn't hold up. Say what's wrong with it. Most of the section is this.
- An argument that does hold up. Work out how it's built, because you're about to be asked to describe it rather than fault it.
- A set of facts. Nothing is being argued and there's nothing to attack. Work out what the statements guarantee.
Noticing which one you have is most of the battle, because the reading habits that earn points on one will lose them on another. Hunt for a flaw in a sound argument and you'll be shopping for an answer choice that names a defect that isn't there. Argue with a set of facts and you'll reject the right answer for being obvious.
Four things a question can ask you to do
With that in hand, the nineteen types sort into four families by what the question wants done:
- Structural analysis — describe what the argument is doing, without judging whether it's any good.
- Argument evaluation — find what would make the argument stronger, weaker, or testable.
- Assumption analysis — find what the argument is taking for granted.
- Deductive inference — work out what does or doesn't follow from what's on the page.
Read the rest of this as a map of what the test asks, not as a set of instructions to run. The method for actually working a question is in analyze, predict, eliminate.
Structural analysis: what is this argument doing?
These questions ask you to describe an argument's anatomy. Most of them don't care whether the argument is convincing; they care what it is made of. This family is where sound arguments show up most often, and where arriving with your flaw-hunting habits switched on will cost you.
Flaw in the Reasoning
Names the gap in the abstract. "Which one of the following most accurately describes a flaw in the argument's reasoning?"
Predict by saying the gap in plain language, then look for the choice that says the same thing in the LSAT's formal vocabulary. The trap is a choice that describes a real, recognizable logical flaw that this particular argument didn't commit. Those choices are correct-sounding precisely because they're textbook.
Try this one:
Archaeologist: At every ancient Varnese site excavated so far, diggers have unearthed hundreds of intricately crafted clay pots, yet scarcely any wooden objects, and the handful of wooden items recovered are crude. The natural conclusion is that the Varnese were highly skilled potters but only rudimentary woodworkers.
Which one of the following most accurately describes a flaw in the argument's reasoning?
- It infers that the Varnese placed little value on the craft of woodworking solely from the absence of any direct evidence that they valued it at all.
- It overlooks the possibility that one kind of object survived far better than another, so the recovered finds may misrepresent the Varnese's true skills.
- It assumes that because crude woodworking is found alongside skilled pottery at these sites, the one must somehow have been the cause of the other.
- It relies on the word "crafted" in one sense in stating its premises and in a quite different sense in stating its conclusion about the Varnese.
- It draws a sweeping conclusion about an entire ancient people from the artifacts that happened to be unearthed at just a single one of their settlements.
Show the answer
B is correct. The evidence is about what survived in the ground; the conclusion is about what the Varnese could make. Wood decays and fired clay doesn't, so the scarcity and crudeness of the wooden finds may be a fact about preservation rather than a fact about skill. The argument treats what was dug up as a fair sample of what was originally produced.
A swaps the conclusion for a different one, since the archaeologist claims the Varnese lacked woodworking skill, not that they didn't value woodworking. C names a causal confusion the argument never makes; the two crafts are treated as separate measures, not as cause and effect. D alleges an equivocation, but "crafted" means the same thing throughout. E is the closest thing to a real second-place answer, and it fails on one word: the stimulus says "every ancient Varnese site excavated so far," not one site.
Notice that all four wrong answers name flaws that genuinely appear on the LSAT all the time. That's the type's signature difficulty. You cannot pick by asking "is this a real flaw?" You have to ask "is this this argument's flaw?"
Method of Reasoning (Argument)
Describes the argument's strategy, not its content. "The argument proceeds by…" Predict in structural terms before looking: it establishes a general rule and applies it to a case, or it rejects a hypothesis by pointing to a counterexample. Right answers are written at that level of abstraction; wrong ones usually describe a method the argument didn't use, or re-state the content rather than the method.
Method of Reasoning (Role of Statement) and Argument Part Identification
Point at one sentence and ask what job it does. "The claim that… plays which one of the following roles?"
Before reading the choices, decide two things: is the referenced statement a premise, the main conclusion, or an intermediate conclusion (something the argument supports and uses to support something else)? And is it something the author endorses, or a view the author is arguing against? Wrong answers on these questions frequently get the direction right but the level wrong, calling an intermediate conclusion the main one.
Parallel Reasoning (Valid) and Parallel Flaw
Ask you to find the answer whose logical structure matches the stimulus. The subject matter will always be different, and the resemblance in topic is bait.
Strip the stimulus to a skeleton before you read the choices, something like all A are B; this is an A; so this is a B, and match on that. For Parallel Flaw, the match has to include the error itself: the right answer commits the same mistake, not merely some mistake. These are among the most time-expensive questions on the section, and skipping one to bank ninety seconds for two others is often the correct play.
Argument evaluation: what would change it?
Here you're not describing the argument, you're acting on it. Every question in this family runs through whatever the argument was leaning on.
Strengthen
"Which one of the following, if true, most strengthens the argument?" Predict something that closes the gap, usually by ruling out an alternative explanation or confirming that the evidence transfers to the conclusion's claim. Note that the right answer does not need to prove the conclusion. It only needs to help. A choice that merely restates a premise adds nothing and is a common wrong answer.
Weaken
"Which one of the following, if true, most weakens the argument?" Predict something that makes the gap worse: an alternative cause, a counterexample, a reason the evidence doesn't transfer. The single most common wrong answer attacks a claim adjacent to the conclusion rather than the conclusion itself, such as whether the plan is worth it when the conclusion was only about whether it works.
Evaluate the Argument
"Which one of the following would be most useful to know in evaluating the argument?" Rarer, and the choices are questions rather than statements. A right answer is one whose two possible answers pull in opposite directions: learning it one way would shore the argument up, learning it the other way would damage it. If a choice's answer wouldn't change your assessment either way, it's out.
Paradox (Resolve, Reconcile, Explain)
"Which one of the following, if true, most helps to resolve the apparent discrepancy?" The odd one out in this family: there's no argument, just two facts that sit uncomfortably together. State the tension precisely, as in X should have led to Y, but Z happened instead, then look for the choice that lets both facts be true at once. Wrong answers typically make the puzzle worse, or explain only one side of it.
Assumption analysis: what is it taking for granted?
The family that trips up the most people, because two of its types sound identical and behave completely differently.
Necessary Assumption
"Which one of the following is an assumption required by the argument?" You're looking for something the argument needs in order to work, not something that would make it airtight.
The test is negation: if you flip the choice to its opposite and the argument collapses, it was required. If you flip it and the argument survives, it wasn't. Because these answers only have to be necessary, they're often strikingly modest, along the lines of "the two groups did not differ in some other relevant way" rather than anything sweeping. Students routinely reject the correct answer for being too weak, then pick a confident-sounding choice that the argument doesn't actually require.
If an argument concludes that a drug helps some patients, it does not require the assumption that the drug helps all of them. Negate "helps all" and the argument is untouched, so that assumption was never necessary. Any word like only, never, always, or must in a Necessary Assumption choice deserves suspicion.
Sufficient Assumption
"Which one of the following, if assumed, allows the conclusion to be properly drawn?" The mirror image. Here you want something enough to make the conclusion follow, and being too strong is perfectly fine.
These questions reward finding the exact missing link: something in the premises, something in the conclusion, and a bridge that doesn't exist yet. Predict the bridge before you look, as in the argument needs "everyone in group X also has property Y," and the matching answer is usually unmistakable.
Principle (Identify) and Principle (Apply)
Principle questions move between a general rule and a specific case. Identify questions give you the case and ask which broad principle it illustrates or justifies; Apply questions give you the rule and ask what follows in a particular situation.
Either way, check scope in both directions: a principle that's narrower than the case won't cover it, and one that's much broader may commit to things the case never showed. Read the conditions in the principle literally, and make sure the facts actually satisfy every one of them.
Deductive inference: what follows?
Now the mode changes. These stimuli are frequently not arguments at all. They're a set of statements you must treat as true. There's nothing to criticize, and the discipline is staying inside what's written.
Must Be True / Most Strongly Supported
"Which one of the following is most strongly supported by the statements above?" Rather than reaching for a single answer in advance, note the pieces that combine: two conditionals that chain, a conditional you can run backward, a quantity that limits another. Then hold each choice against them.
One thing students get wrong here on principle: a choice can be correct without being clever. Anything guaranteed by the statements is fair game, including something a statement already said. A restatement of a premise is guaranteed by the premises, and it's a credited answer more often than people expect, because it gets thrown out for "just repeating the passage." Repeating the passage is not a defect on this type. It's the standard.
During last week's coastal storm, every buoy in the bay that recorded a wave height above four meters also recorded a wind gust above sixty kilometers per hour. Every buoy that recorded a wind gust above sixty kilometers per hour triggered its automatic warning light. Buoy 3's automatic warning light did not trigger at any point during the storm.
Which one of the following is most strongly supported by the statements above?
- Buoy 3 did not record a wave height above four meters during the storm.
- Had Buoy 3 recorded a wave height above four meters, some other buoy's warning light would have triggered.
- Buoy 3 recorded lower wave heights during the storm than any buoy whose warning light triggered.
- Buoy 3 recorded neither a wind gust above sixty kilometers per hour nor any rainfall during the storm.
- Every buoy whose warning light triggered during the storm recorded a wave height above four meters.
Show the answer
A is correct. The rules chain forward: a wave above four meters means a gust above sixty, and a gust above sixty means the light triggered. So a high wave guarantees a triggered light. The one fact you have about Buoy 3 runs the other way, since its light didn't trigger, so read the chain backward: no light means no qualifying gust, and no qualifying gust means no wave above four meters.
E reverses the rules, treating a triggered light as proof of a high wave; a gust alone could have triggered it. C turns that same reversal into a comparison between buoys that the statements never make. D starts correctly, because no qualifying gust does follow, and then bolts on a claim about rainfall that nothing supports. B invents a relationship between one buoy's readings and another buoy's light.
Two habits pay for themselves on this type. First, when you see a conditional, note its contrapositive immediately. A large share of these questions are solved by running a rule backward, as this one is. Second, be ruthless about choices like D, which pair something that follows with something that doesn't. A choice is only correct if all of it is supported.
Must Be False
The inverse and much rarer: which choice is incompatible with the statements. Same skill, reversed target.
Main Point / Main Conclusion
"Which one of the following most accurately expresses the main conclusion of the argument?" Apply the "why" test in the stimulus, decide on the conclusion, then find the choice that paraphrases it. The reliable trap is the intermediate conclusion: a claim that really is supported by the premises, but exists to support something further. Ask what the argument is ultimately for.
Conclusion / Fill-in-the-Blank
The stimulus ends mid-thought, often after "therefore" or "which suggests that." You supply the conclusion the evidence actually licenses. Predict before looking, and keep the prediction modest: the right answer is normally the most cautious claim the premises can carry, not the most interesting one.
Point at Issue / Point of Agreement
Two speakers, and you identify what they actually disagree (or agree) about. The right answer must be something both speakers address and on which they take opposite positions. Most wrong answers fail one half of that: a claim only one speaker mentioned, or one they'd both endorse.
A note on stem wording
Two pairs of stems are worth knowing cold, because the wording is nearly identical and the task is not.
- "required by" vs "if assumed, allows the conclusion to be properly drawn" — necessary versus sufficient. One asks what the argument can't do without; the other asks what would be enough to finish the job.
- "most strongly supported by the statements above" vs "most strongly supports the statements above" — supported by means the stimulus holds up the answer; supports means the answer holds up the stimulus. A surprising number of missed questions are just that reversal.
Read the question carefully enough to know which one you have. That is a different act from reading the question in order to look up a procedure, and it is the one that survives contact with an unfamiliar stem.
What to do with this
Don't memorize nineteen definitions. Practice reacting to stimuli, asking whether this is an argument, whether it holds up, and what these facts guarantee, until that reaction is automatic, and let the question in front of you tell you what to do with the reaction.
Then track your accuracy by type, because the types are not equally hard for any two people. Some students lose most of their points to Parallel Reasoning and Method questions; others are fine there and bleed on Necessary Assumption. Those are different problems, and studying "Logical Reasoning" as one undifferentiated block is how people spend three months practicing the types they were already good at. Types are a good way to read your results. They're a bad way to work a question.
Practice this with Forge180
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