More than anything, it's a way of looking at the world.

I do art.  I love it, and I've supported myself with it over the years.   I have a fair amount of technical ability and I'm very versatile. I can copy anything--would be a good forger.  I've called myself an artist, and even listed it on my tax returns for a couple of years.  But I always feel like a phony, because I lack that essential spark, that fire that is the thing that sets the true artistic personality apart from the rest of us.  My husband once told me that I'd never be a true artist "because I'm not tormented enough."  I know what he means.  Even in my younger days I was more interested in taking a nap than expanding my creative limits.  When I was growing up,  I was offered a chance to go to the High School of Art and Design (and 2 subway tokens a day) if I'd stay in school.  I quit school and got a job in a supermarket because I wanted a steady, reliable income.

That's not the mindset of a "real" artist, I don't think.  I have a certain amount of ability, but I lack the passion.  I'm not willing to sacrifice for my art.  I'm not willing to struggle.  I've had "serious" artists call me a sell-out because I do a bunch of stuff that I don't particularly care for myself, but it sells very well.  It's fun, and I find it very rewarding that people like what I do, but I guess it doesn't say much for my "standards." 

On the other hand, I have a friend who, to me, is the definition of "artist."  She walks, talks, eats, breathes it.  She struggles and sacrifices and scrimps and saves and does without in order to make her art.  She's an art teacher, teaching at 2 different community colleges and a private school (so she can have time off to make her stuff), shows her work, is always submitting stuff to juried exhibits, does performance pieces, hangs stuff in coffee shops, and actively seeks commissions.   She's always scoping out the world around her, constantly on the lookout for stuff to incorporate into her "found" pieces.  She hangs out with a bunch of other like-minded artist-types, who seem to take it all a lot more seriously than I do.
 
 It's hard to put into words, but she has that undefinable "something" that I lack.  Art is what I do; it's who she is.  She's got the "eyes that burn with a fire of a thousand inner visions," to paraphrase Don Quixote."  My eyes would just as soon waste time poking around on Askville.

Those are two ways of "being" an artist.  But by far the most important criteria is not definitively linked with "talent" or "ability."  Or artistic output.  It is the creative mindset---how we see the world, how we see new possibilities in the ordinary, and find excitement in the mundane.  The artistic personality has an infinite sense of wonder and an appreciation of beauty (or the awareness of the lack of it).   Creative people are curious.  They notice things, question things, and are almost compelled to take them apart and see how they work.  In that way I believe I am an artist.  Even if you can't draw anything but a deep breath, if you've ever wondered, "What if...,"  or if you often see things differently than most people, I think you know what I mean.