in the priori explanation, what if you were the very first person in the world to discover a three sided figure, and you didn't name it a triangle, you named it a fork, if a fork is now the name you give to every three sided figure, couldn't it be inferred that through your sense of sight you found a similarity in objects and were able to group them and give them a name, many things out there were discovered and named by people who first made observations using their senses