A real croissant
If we have never had a real croissant, how do we know whether we like them?
We may have just had pieces of pastry rolled with almost no butter and left to become soggy and sad. And that is not something to like.
Getting to Paris to have a real one before we have an opinion is also ridiculous.
So we are stuck with learning what something is as much as we can, before we decide if we like it or not.