logic: contrapositives

contraposition can be reduced to obversion and conversion. to form the contrapositive of a given proposition, we place its subject term with the complement of its predicate term and we replace its predicate term with the complement of its subject term.

from text:

1. contraposition is a valid form of immediate inference when applied to A propositions and to O propositions.
2. for I propositions the contrapositive is not generally valid
3. for E propositions, not valid
   

i need to flesh out 2 and 3 more, but for now i am tired.

so, the complement of P is not P.

state the contrapositives and indicate which are equivalent to the original

1. all journalists are pessimists
2. some soldiers are not officers
3. all scholars are nondegenrates
4. all things weighing more than fitty pounds are objects not more than four feet high.
5. some non-citizens are not nonresidents
   

so, to state the contrapositve:

subject term with the complement of its predicate term and we replace its predicate term with the complement of its subject term.

hm, that seems like swap and negate:

1. all non-pessimists are non-journalists
2. some non-officers are non-soldiers
3. all degenerates are non-scholars
4. all non-objects ... are not things weighing more ...
5. some residents are citizens