29. Explain the exact nature of the relation between two Contradictory propositions; and define Conversion by Contraposition, determining what kind of propositions admit of such conversion.
Give the contradictory and the contrapositive of each of the following propositions:—
(a) All equilateral triangles are equiangular;
(b) No vertebrate animal has jaws opening sideways;
(c) Wherever A and B are both present, either C or D is also present. [S]
30. Define Obversion and Inversion, and apply these processes also to the above three propositions.
31. Propositions can be understood either in extension or in intension. Explain this, and discuss the relative value of the two interpretations. [S]
32. Distinguish between real and verbal propositions; and explain the importance of the distinction.
33. Illustrate the process called 'change of Relation.'