I'm having trouble with "The Only"—is it the same as "Only" and "Only If"?
Yeah, "the only" is the tricky one.
As we've discussed, only and only if are arrows.
The only, on the other hand, means the same thing as All.
So, Only an idiot would buy that record, which clearly means the same thing as Buy that record only if you're an idiot, is symbolized the same way:
Record → Idiot
However, those are different from The only idiots here are the people who bought that record, which is the same as saying All idiots here bought that record:
Idiot → Record
All of this to say just remember that the only means all and you'll be fine.