what are the requirements of being a philosopher?

[No comment on my lengthy sabbatical from writing in this space.]

About a month ago, I started to ask myself whether someone has to be "smart" to be a philosopher. The canon of the history of western philosophy is peopled entirely by smart people (okay, except for Kant). But a philosopher is not just a smart person, obviously, and the kinds of smartness philosophers exhibit seem like they have a particularity to them that you don't necessarily find among other people, smart or not.

I know lots of really smart people, lots of people with doctoral degrees who do scientific research or academic scholarship, and teach at universities. The way philosophers are smart seems different to me than the way other people are smart. Others notice this too, or seem to, whenever they raise eyebrows at the kinds of questions philosophers raise. How much of this is the smartness, and how much if it is the particularly forms of reflection philosophers are prone to?

Here's a first hypothesis. There are pretty obvious cultural and ethnic attributes exhibited by philosophers trained in the western canonical tradition, and those both favor and contribute to the development of a certain kind of smartness. So, the relation between smartness and philosophy is at least partly culture-bound, and not necessarily essential to philosophy as such.

If we strip away the culture-bound aspects, would there still be a smartness pertinent to philosophy as such?