Take the statements below to be true, even if they differ from known facts. Which of the conclusions follow logically from them?
Statements:
1. All roses are flowers.
2. Some plants are not flowers.
Conclusions:
I. Some flowers are not plants.
II. Some plants are not roses.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Only conclusion II follows
A conclusion follows only if it is true in every diagram that fits the statements; each class named in a statement is taken to have members. “Some X are not Y” cannot be read the other way round.
“All roses are flowers”: the circle of roses lies inside the circle of flowers
“Some plants are not flowers”: part of the plants lies outside the flowers; the rest of the plants may lie anywhere, even over all the flowers
Conclusion I: Some flowers are not plants. — Does not follow. The plants may cover all the flowers, as in the diagram; then every flower is a plant.
Conclusion II: Some plants are not roses. — Follows. The plants that are not flowers cannot be roses, because every rose is a flower.