| Phil. 1: Introduction to Logic | |
| Schedule | |
| Answer Key | |
Exercise 5.4
1. Some non-T are M. (conv., obv.) Some M are not T.
All non-I are non-M. (contrapose) All M are I.
Some I are T. Some I are T.
Invalid
Drawing affirmative conclusion from a negative premise
2. All S are R. All S are R.
Some non-R are C. (conv., obv.) Some C are not R.
Some C are non-S. (obvert) Some C are not S.
Valid
3. All non-S are non-W. (contrapose) All W are S.
All P are W. All P are W.
All P are S. All P are S.
Valid
4. Some I are C. Some I are C.
All C are non-P. All C are non-P.
Some non-I are not P. (contrapose) Some non-P are not I.
Invalid
Illicit major; drawing negative conclusion from affirmative premises
5. All W are non-D. (obvert) No W are D.
All D are non-S. (obvert) No D are S.
No non-W are S (conv., obv.) All S are W.
Invalid.
Exclusive premises; drawing affirmative conclusion from negative premises
6. No F are D. No F are D.
No non-F are C. (conv., obv.) All C are F.
All C are non-D. (obvert) No C are D.
Valid
7. All non-M are non-E. (contrapose) All E are M.
Some P are not M. Some P are not M.
Some P are non-E. (obvert) Some P are not E.
Valid
8. All S are non-E. (obvert) No S are E.
Some non-S are U. (conv., obv.) Some U are not S.
Some U are not E. Some U are not E.
Invalid
Exclusive premises
9. All D are non-I. (obvert) No D are I.
All non-D are non-C. (contrapose) All C are D.
No C are I. No C are I.
Valid
10. No D are V. No D are V.
Some S are non-D. (obvert) Some S are not D.
Some non-V are S. (conv., obv.) Some S are not V.
Invalid.
Exclusive premises
Exercise 5.4
1. Some non-T are M. (conv., obv.) Some M are not T.
All non-I are non-M. (contrapose) All M are I.
Some I are T. Some I are T.
Invalid
Drawing affirmative conclusion from a negative premise
2. All S are R. All S are R.
Some non-R are C. (conv., obv.) Some C are not R.
Some C are non-S. (obvert) Some C are not S.
Valid
3. All non-S are non-W. (contrapose) All W are S.
All P are W. All P are W.
All P are S. All P are S.
Valid
4. Some I are C. Some I are C.
All C are non-P. All C are non-P.
Some non-I are not P. (contrapose) Some non-P are not I.
Invalid
Illicit major; drawing negative conclusion from affirmative premises
5. All W are non-D. (obvert) No W are D.
All D are non-S. (obvert) No D are S.
No non-W are S (conv., obv.) All S are W.
Invalid.
Exclusive premises; drawing affirmative conclusion from negative premises
6. No F are D. No F are D.
No non-F are C. (conv., obv.) All C are F.
All C are non-D. (obvert) No C are D.
Valid
7. All non-M are non-E. (contrapose) All E are M.
Some P are not M. Some P are not M.
Some P are non-E. (obvert) Some P are not E.
Valid
8. All S are non-E. (obvert) No S are E.
Some non-S are U. (conv., obv.) Some U are not S.
Some U are not E. Some U are not E.
Invalid
Exclusive premises
9. All D are non-I. (obvert) No D are I.
All non-D are non-C. (contrapose) All C are D.
No C are I. No C are I.
Valid
10. No D are V. No D are V.
Some S are non-D. (obvert) Some S are not D.
Some non-V are S. (conv., obv.) Some S are not V.
Invalid.
Exclusive premises