§ 711. A can only be converted per accidens, as above.
The original proposition
'If A is B, C is always D'
is equivalent to the simple proposition
'All cases of A being B are cases of C being D.'
This, when converted, becomes
'Some cases of C being D are cases of A being B,'
which, when thrown back into the conjunctive form, becomes
'If C is D, A is sometimes B.'
§ 712. This expression must not be misunderstood as though it contained any reference to actual existence. The meaning might be better conveyed by the form