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Critical thinking Categorical proposition and logical squares (logical…
Critical thinking Categorical proposition and logical squares
logical squares
universal affirmative = every , all =
A
particular affirmative = some =
I
universal negative = none =
E
particular negative = some.. not =
O
--> predicate/verbs in affirmative proposition = always particular/ specific/ expanding concept of subject
--> predicate/verbs in negative proposition = universal/ unspecific in that minimize the concept of the subject by excluding whole groups
Contradiction
"A" and "O"
True "A" = False "O"
--> double negative (false O) = same as true A
False "A" = True "O"
"E" and "I"
True "E" = False "I"
False "E" = True "I"
--> double negative (false E) = same as true I
CANNOT BE TRUE NOR FALSE AT SAME TIME !!
--> has to be different !!!
Contrary (A vs E)
CANNOT BE TRUE AT SAME TIME!!
Can be both false at the same time or different (one true the other false)
If either "A" or "E" = true
--> then the other has to be false!
If either "A" or "E" = false
--> the other has to be invalid/undetermined as it could be either true or false and they cannot be true at same time !
Subcontrary (I vs O)
CANNOT BE FALSE AT SAME TIME !!
Can be both right or different (one true the other false)
If either "I" or "O" = true
--> the other has to be invalid/undetermined as it could be either true or false and they cannot be true at same time !
If either "I" or "O" = false
--> the other has to be true as it cant be wrong :3 !!
Subaltern (A vs I ; E vs O)
IF universal proposition ("A" or "E") is true,
then the particular proposition (for A = " I"; for E = "O") is also always true
If the particular proposition ("I" or "O") is false,
then the universal proposition ( for I = "A" ; for O = "E") is also always false
Venn Diagramms
Conversion
Works only for "E" and "I"
subject and predicate is changed
Obversion
Works for all (A,I; E,O)
first : quality (all/no) is changed
--> if all then change to No and vice versa
second: reversing the predicate/verb (attaching "no" to it)
--> if subject = book then change it to no book!
All books are nice --> No books are not-nice
horses are mammals --> no horses are not-mammals
Some marine animals are fish --> Some marine animals are not no-fish
Contraposition
Works for "A" and "O"