Wow, so many comments from people that clearly didn't bother reading the article (all the way through). I suppose its understandable, I too had to fight the temptation to hit the back button and angrily type out "its just a definition!". Luckily I decided to actually read the whole thing through, notice that the author is quite aware of this, and be treated to a really interesting history of math.
Agreed. It is an interesting article to read. The survey cited is also interesting in its own right [1]. We often forget that ideas we find trivial and intuitive are only so because it took the work of many more people and centuries to hone their ideas which at that time would be have been new and ambiguous. This is especially true with mathematics because a lot of the field focuses on getting the right abstractions to complex ideas which when done correctly seem "trivial, natural, and straightforward." Also see the history of calculus [2].
