Treat the words as exact rules
Logical deduction asks which conclusion must follow. Treat each premise as true. Names such as Amber and Birch are just group labels, not facts about real objects.
All Amber items are Birch items puts every Amber item inside Birch. It does not say that every Birch item is Amber.
Some means at least one. All and No do not guarantee that any items exist. A group boundary in the diagram shows a relationship, not an item.
Follow the whole chain
Take these premises as true:
- All Amber items are Birch items.
- No Birch items are Coral items.
Any Amber item would have to be Birch. But Birch and Coral cannot overlap. So no Amber items can be Coral items.
This conclusion holds even if the Amber group is empty. We have ruled out an overlap; we have not claimed that an Amber item exists.
Separate inclusion from existence
Use only these new premises:
- All Amber items are Birch items.
- All Birch items are Coral items.
Trace what must be true of any Amber item. Then check whether either premise says that an Amber item actually exists.
Choose the conclusion that is guaranteed, not one that could happen to be true.
Try it
Which conclusion must follow?
- Some Amber items are Coral items.
- All Amber items are Coral items.
Show the answer
All Amber items are Coral items.
Every Amber item would be Birch, and every Birch item would be Coral. So all Amber items are Coral items. This does not claim that any Amber items exist.
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