in contemporary texts of islamic logic, the “subject-obversion” has been introduced as a rule on basis of which one can replace the subject term of a categorical proposition with its complement and change both quality and quantity of the proposition. thus from an a-proposition such as “all a is b”, one can infer “some not-a is not b”. well, let’s take that a is included by b but not vice versa,...

some contemporary logicians have introduced a new simple method of logical consequences and reduced all immediate arguments to conversion and obversion. by dint of positive and infinite terms, one of the logicians, reza akbari, increased the four traditional quantified propositions to 32 ones: the 4 well-known positives, 4 subject-infinites, 4 predicate-infinites, 4 two-sided-infinites, and the...