The inference students miss
When two "most" statements describe the same group, they force an overlap: "Most A are B" plus "Most A are C" guarantees that "Some B are C." This is one of the most-tested and most-missed inferences on Must Be True questions, and it follows from simple counting.
The reason it slips past people is that nothing in the two sentences mentions B and C together. The link is hidden. But because both majorities are carved out of the same A, they cannot avoid each other — and the test rewards students who see that.
This guide covers the combinations that produce a valid inference, the ones that look valid but fail, and two quirks of "most" and "some" that decide whether a chain holds.
Why two majorities must overlap
"Most" means more than half. If more than half of A are B, and more than half of A are C, the two groups are each larger than half of A — so they cannot fit inside A without sharing members. At least one A must be both B and C.
Picture 100 members of A. If 60 are B and 60 are C, the B group and the C group together would need 120 slots, but there are only 100 members. The overflow — at least 20 — must be members that are both. That forced overlap is your "some B are C."
Note what you get and what you don't. You get "some" (at least one), which is all the overlap guarantees. You do not get "most B are C" — the overlap could be a minority of B. Claiming more than "some" is the classic over-reach.
The combinations that work
The valid combinations all share a feature: they pin the connection to a common term that the quantifiers genuinely cover.
| You're told | You can infer | Why |
|---|---|---|
| Most A are B; Most A are C | Some B are C | Two majorities of A must overlap |
| All A are B; Most A are C | Some B are C | The C-majority of A are also B |
| All A are B; All B are C | All A are C | Standard conditional chain |
| Most A are B; All B are C | Most A are C | The A's that are B are all C |
The first three are the workhorses. The last one is worth memorizing because it preserves "most": when an "all" statement carries the B's all the way to C, the original majority of A rides along.
The combinations that look valid but aren't
"Most A are B" plus "Most B are C" does NOT give you "Most A are C," and it does not even give you "Some A are C." The two majorities are taken from different groups — one slice of A, one slice of B — and they need not overlap in the right place. This is the single most common trap.
Concretely: most dogs are friendly; most friendly things are small. It does not follow that any dog is small. The "friendly" dogs and the "small friendly things" can be entirely different friendly things. The shared term sits in the wrong position to force a link.
"Most" also does not chain like a conditional. You cannot string "most ... most ... most" the way you string "if ... then." Each "most" is anchored to its own subject, and the moment the common term shifts roles, the inference dies.
Two quirks: reversibility and strength
"Some" is reversible: "some A are B" means exactly the same as "some B are A." So once you derive "some B are C," you also have "some C are B" for free — useful when the answer choice flips the order.
"Most" is not reversible. "Most A are B" tells you nothing about what share of B are A. Most senators are lawyers, but hardly any lawyers are senators. Treating "most" as a two-way street is a reliable way to pick a wrong answer.
Keep the strength straight, too. Overlap inferences yield "some," not "most." The only way to keep "most" through a combination is to ride an "all" statement, as in the fourth row of the table above.
Worked example
Stimulus: "Most of the museum's Renaissance holdings are on loan. Most of the museum's Renaissance holdings have been restored in the last decade."
Both statements are majorities of the same group — the Renaissance holdings. So the overlap rule fires: some on-loan Renaissance pieces have been restored in the last decade. That is a valid Must Be True answer.
What is not supported: "Most restored pieces are on loan" (over-claims strength and reverses "most"), or "All on-loan pieces were restored" (over-claims to "all"). The only safe inference is the modest "some," stated in either order.
The common mistake
The biggest mistake is chaining "most" statements through a shared term that has changed position — "most A are B, most B are C, therefore something about A and C." Unless one link is an "all," nothing about A and C follows.
The second mistake is reversing "most." "Most A are B" never becomes "most B are A." Only "some" and "all" relationships support the reversals you might be tempted to make, and even "all" only reverses to "some."
The third is upgrading the conclusion from "some" to "most" or "all." Overlap guarantees a single shared member; demand no more than that from it.
Frequently asked questions
Can you chain "most" statements like conditionals?
No. "Most A are B" plus "Most B are C" supports nothing about A and C. "Most" only combines safely when the two statements share the same subject (most A ... most A ...), or when an "all" statement carries the term through. Conditional-style chaining is for "all" statements.
Does "most" reverse?
No. "Most A are B" tells you nothing about how many B are A. Most senators are lawyers, but very few lawyers are senators. Only "some" reverses freely ("some A are B" = "some B are A").
What exactly does "most A are B" plus "most A are C" give you?
It guarantees "some B are C" (equivalently, "some C are B"). Both majorities are carved from the same A, so they must overlap by at least one member. You get "some," never "most" or "all."
Is "some" reversible?
Yes. "Some A are B" and "some B are A" are identical claims — at least one thing is both. That lets you match an answer choice that states the overlap in the opposite order.
Related Verbloom guides
Want LSAT logic to feel visual?
Verbloom turns argument structure into short visual lessons, drills, and explanations built for actual score movement.