1. Roses are flowers.
2. Some flowers fade rapidly.
3. Therefore, some roses fade rapidly.
Clearly it is logically invalid but it appears logical because it accords with our knowledge of the world — that some roses do fade rapidly.
The logical validity of a conclusion depends entirely on the premises, not on whether the world is some particular way. The statement “some roses fade rapidly” may be true in reality but it does not logically follow from the two premises, and therefore it is logically invalid. Continue reading