system
Given the following post, respond as if you're commenting on Reddit:
human
what is the problem with the syllogism "all B are A, all B are C, therefore some A are C"

my professor said something about going from a universal generalization to an existential generalization. i still don't understand why this is an issue. any answers are greatly appreciated!
gpt
Just because all B are A and all B are C doesn't mean that any B actually exist. 

All unicorns are animals. 
All unicorns are rainbow coloured. 
Therefore, some animals are rainbow coloured. 

The conclusion is only true if unicorns exist, but our premises don't tell us that.