And in order for an I proposition to be false, no members can be common between the two kinds, which will equally make the converse of the original I proposition false. Conversion is legitimate for I propositions. The fact that E and I are symmetrical in distributing or not distributing their terms is significant here. In the case of the unsymmetrical A propositions where only the subject is distributed, converting results in a claim about every member of the former predicate class. But the basis of the new claim is supposed to be the original claim which did not make a claim about every member of the predicate class.
Nothing justifies the stronger claim about that class.
A propositions may be legitimately partially converted. Partial conversion, then involves taking the subaltern first and then converting. Partial conversion only is legitimate for true A propositions. The compliment of a class is the class of everything not in the original class. The class of non-dogs is the compliment of the class of dogs.