Question about Syllogisms




I) No picnic is blades

II) Some blades are CD's


I) No CD is a picnic

II) Some picnics are definitely not CD's

Which one of these conclusions follow? I stated that conclusion 2 follows but the practice test I am doing says neither conclusions follow? Is the practice test wrong or am I?

Sabeeh Siddiqi

Posted 2017-08-03T02:21:25.613

Reputation: 21

1Neither. Counterexample to I) : No cat is a dog. Some dogs are males. Therefore: No male is a cat. – Mauro ALLEGRANZA – 2017-08-03T06:04:05.927

1Similar for II). – Mauro ALLEGRANZA – 2017-08-03T06:58:54.133

What does it mean to say that 'no picnic is blades'? It doesn't appear to mean anything, unless the sentences are 'well-formed' grammatically, and make sense semantically it doesn't much matter what logic is applied. – Mozibur Ullah – 2017-08-04T02:31:41.637



Conclusion (I) does not follow. The syllogism is EIE in the fourth figure. No P are M; Some S are M; thus No S are P. The problem is that the minor term (S, CDs) is distributed in the conclusion but not in the minor premise.

Conclusion (II) does not follow. Here, the premises are inverted, as the predicate has been placed in the second premise. Reordering the premises shows that the example is IEO in the first figure. Some M are P; No S are M; thus Some S are not P. The problem is that the major term (P, CDs) is distributed in the conclusion but not in the major premise.

Mark Andrews

Posted 2017-08-03T02:21:25.613

Reputation: 4 397