Still, an exception may be made by admitting a bi-designate conclusion:
Some P is M; Some S is not M: ∴ Some S is not some P.
(ii) If one premise be particular, so is the conclusion.
For, again, if both premises be affirmative, they only distribute one term, the subject of the universal premise, and this must be the middle term. The minor term, therefore, is undistributed, and the conclusion must be particular.
If one premise be negative, the two premises together can distribute only two terms, the subject of the universal and the predicate of the negative (which may be the same premise). One of these terms must be the middle; the other (since the conclusion is negative) must be the major. The minor term, therefore, is undistributed, and the conclusion must be particular.
(iii) From a particular major and a negative minor premise nothing can be inferred.
For the minor premise being negative, the major premise must be affirmative (5th Canon); and therefore, being particular, distributes the major term neither in its subject nor in its predicate. But since the conclusion must be negative (6th Canon), a distributed major term is demanded, e.g.,
Some M is P;
No S is M:
∴ ———
Here the minor and the middle terms are both distributed, but not the major (P); and, therefore, a negative conclusion is impossible.