Some, Most, and All on the LSAT: Quantifier Logic Made Simple
Some, most, and all behave very differently in LSAT inferences. Learn what each quantifier lets you conclude, why most plus most can chain but some cannot, and the valid inference patterns to memorize.
2026-05-27 · 8 min read
Why quantifiers trip people up
The LSAT loves the words some, most, and all because students treat them loosely in everyday speech. On the test, each has a precise meaning, and confusing them produces invalid inferences that the wrong answers are built around.
Some means at least one. Most means more than half. All means every single one. Getting these exact definitions in your head is the first step.
What each one lets you infer
All statements are the strongest and chain cleanly: if all A are B and all B are C, then all A are C. They also have contrapositives, since all A are B means anything that is not B is not A.
Some statements are symmetric and weak: if some A are B, then some B are A. But some does not chain. From some A are B and some B are C, you can conclude nothing about A and C, because the overlapping members might be different.
Most statements are stronger than some but do not reverse. If most A are B, you cannot conclude most B are A.
The valid most plus most pattern
There is one famous valid inference. If most A are B and most A are C, then at least one B is also a C, in other words some B are C. The reason is that two groups each containing more than half of A must overlap within A.
This is the inference the test rewards. Memorize it: most A are B, most A are C, therefore some B are C. Note that the two most statements must share the same subject, A.
Combining quantifiers with conditionals
Quantifier questions often mix with conditional statements. If all A are B is the same as the conditional if A then B. That lets you connect a some or most statement to a chain of conditionals.
For example, most A are B, and all B are C, gives you most A are C, because every B is also a C, so the more-than-half of A that are B are also C. A universal rule can extend a most statement forward, though never backward.
Practice the patterns
Drill the four facts until they are automatic: all chains and contrapositives; some reverses but never chains; most neither reverses nor chains alone; most plus most with a shared subject yields some. When you can apply these without hesitation, formal-logic inference questions become quick points.
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