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