E. 1.3 ContrapositionThis is a kind of education which results from

a formulation of a new proposition whose subject term is the contradictory of the predicate term in the original proposition.

In principle, contraposition is a product of both conversion and obversion . Thus like conversion , contraposition involves an interchange of the subject and predicate terms, and like obversion , it involves either the use or removal of negatives which affects the copula and the terms.

We can immediately see that there are two types ofContraposition. They are Partial or Simple andComplete.

Partial Contraposition consists the formulation of anew proposition (contraposit) through the following:

a. Its (contraposit) subject is the contradictory of thepredicate term of the original proposition(contraponend), Ex. (Contraponend) All whales are mammals. (A) to

Su Pp(Contraposit) No non-mammals are whales. (E)Su Pu

b. The quality of the contraponend is changed in the

contraposit; andEx. (Contraponend) No fishes are dogs. (E) to

Su Pu(Contraposit) Some non-dogs are fishes. (I)

Sp Pp

c. The predicate term in the “A” proposition is changed

to “E”, while “E” proposition to “I”, and an “O”proposition to “I”.Ex.(Contraponend) Some students are not

studios.(O) toSp Pu

(Contraposit) Some non-studious are not non-students.(E)

Sp Pp

Complete Contraposition. a new proposition

(contraposit) is formulated through the following steps:

a. The subject term in the contraposit is the contradictory of the predicate term in the contraponend ,

b. The quality of the contraponend is not changed in the contraposit ; and

c. The predicate term in the contraposit is the contradictory of the subject term in the contraponend.

In complete contraposition, an “A” proposition is

changed to A, then E to O, and O to O.

1. (Contraponend) All whales are mammals. (A) toSu Pp(Contraposit) All non-mammals are non-whales.(A)Su Pp

2. (Contraponend) No fish is a dog. (E) to Su Pu(Contraposit) Some non-dog is not a non-fish. (O)Sp Pu

3. (Contraponend) Some students are not studious.(O) toSp Pu(Contraposit) Some non-studious are not students.(O)Sp Pu