LSAT Valid/Invalid Argument Forms
Invalid Form #4
All A's are B's. Most B's are C's. Therefore, most A's are C's. A ---> B most C ---------- A most C
Valid Form #7
All A's are B's. Some A's are C's. Therefore, some B's are C's. A ---> B A some C -------- B some C
Invalid Form #1 (Affirming the Necessary)
All Jedi use the Force. Dock uses the Force. Therefore, Dooku is a Jedi. A ---> B B ------- A
Valid Form #1 (Affirming the Sufficient)
All boys like to play computer games. Tom is a boy. Therefore, Tom likes to play computer games. A --> B A --------- B
Valid Form #2 (Denying the Necessary)
All doctors treat patients. Hercules doesn't treat patients. Therefore, Hercules is not a doctor. A ---> B /B -------- /A
Invalid Form #3
All dogs are cute. Some cute things are lovable. Therefore, some dogs are lovable. A ---> B some C ----------- A some C
Valid Form #8
All stars are bright. Most stars are supermassive. Therefore, some things that burn bright are supermassive. A ---> B A most ---> C --------- B some C
Invalid Form #2 (Denying the Sufficient)
All tragedies are sad. I'm not a tragedy. Therefore, I'm not sad. A ---> B /A ------ /B
Valid Form #6
All turtles know kung fu. All turtles are named after Italian artists. Therefore, some things that know kung fu are named after Italian artists. A ---> B A ---> C -------- B some C A ---> C B ---> C -------- /A some /B
Valid Form #3 (Transitive)
Everyone has the capacity to love. To love requires compassion. Therefore, everyone has compassion. A ---> B---> C ---------- A ---> C
Invalid Form #6
Most A's are B's. Most B's are C's. Therefore, some A's are C's. A most B most C ---------- A some C
Valid Form #5
Most cats are aloof. Everything that's aloof is arrogant. Therefore, most cats are arrogant. A most B ---> C ---------- A most C
Valid Form #9
Most turtles are delicious to eat. Most turtles know kung fu. Therefore, some things that are delicious to eat know kung fu. A most B A most C ---------- B some C
Invalid Form #7
Some A's are B's. Some A's are C's. Therefore, some B's are C's. A some B A some C ---------- B some C
Invalid Form #5
Some A's are B's. Some B's are C's. Therefore, some A's are C's. A some B some C ---------- A some C
Valid Form #4
Some dogs are cute. All cute things are lovable. Therefore, some dogs are lovable. A some B --> C --------- A some C