We perceive a difference between "but" and "yet"; that is, they're not perfectly interchangeable.
So how can the difference be defined, anyway? They're both conjunctions.
I was trying to explain to someone why I had used "yet" instead of "but" to join two independent clauses, but I realized that I couldn't explain why.
I asked quite a few experts and did not get any thoughts.
And so...here we are on the internet. Begin!