Posted by Mike on .
All flies are winged creatures.
All butterflies are winged creatures
Therefore, all butterflies are flies
I believe this is an invalid syllogism, not 100% sure. Can you explain why it would be valid or invalid please

Critical Thinking 
jim,
A valid syllogism is:
All A are B
C is A
therefore
(since C is A and all A are B)
C is B
The nonsyllogism above is:
All A are B
All C are B
Therefore all A are B.
Erm, no.
Spot the difference. Here's one of the same form:
All fish are animals
All birds are animals
Therefore all fish are birds.