Thanks for addressing this head-on since I feel many people don't. It's a rather painful and prickly topic. I once asked an indie filmmaker this very same question. He looked at me and told me that it's extremely hard to make an accurate assessment on this. Why? Because of subjectivity and because every year films, books, and other media that are not "that great" come out and perform exceedingly well. What I think is completely awful goes on to launch careers and record-breaking success. He proved this point to me when he said, "If I had gotten to talk to Niki Caro I would've told her not to make Whale Rider because I thought it was awful" - and yet I personally disagreed, finding the film to be a poignant and culturally compelling story. Whenever my inner critic starts to strangle me, I momentarily let him win by telling him that I have no talent and I am wasting my time. And my work is polarizing, receiving extremely negative reviews by some, and awards from others. Even as a writer, if you plan on having an extended career, it is highly unlikely that you will be churning out Nobel-worthy work year after year. Even among the greats there are duds that they've produced. So I've resigned myself to not think about this question and only focus on the very tangible option of working day in and day out to hone my craft in the hopes of one day churning out something that can be considered beautiful.

First, this TED Talk from Elizabeth Gilbert in which she talks about genius, creativity and failure. Second, the swear-laced pep talk Talent = 10,000 Hours + Luck from Kirby Ferguson of Everything is a Remix fame.

People are always saying to me "I'd really like to write, but I'm waiting for the right idea". By which they seem to mean 'any idea at all'. Invariably, they never write anything, or certainly never finish it. And all the good writers I know have more ideas than they can keep up with. So as one measure of talent, I nominate: having ideas. Filmable, coherent ideas that are 'commercial' - which may mean half a billion dollars worldwide and Tom Cruise in the lead, or it may mean indie, arthouse stories that succeed with their target audience and win awards. Either way, ideas that feel and sound like real movies. If you're having ideas that you pitch to people and they say "Hey, that sounds like a good movie!", then in my opinion, you've almost certainly got talent.

This might sound ridiculous and/or pretentious, but maybe, almost like love, you just know? If you have the chops, you know. If you have your doubts, you could make it with a bit of luck. If you're not confident, i doubt you'd stand a chance.

The best athletes are also the hardest-working. That is not a coincidence. I've always believed that screenwriting is 50% talent, 50% hard work, and 50% luck. That doesn't make any sense, but what in this industry does? Just keep working hard. If you can't do that, that's when you know you don't have what it takes.

I think I'll have to blog my full answer later, but in short: Who cares? If we're using the technical definition of "talent" (an innate, unchangeable ability) -- then it doesn't matter. You can't change it anyway. Why worry? Get out of your head about it. As to when to quit... that's a little more difficult to answer. You might be one script away. You might be 100 scripts away. Part of me wants to be glib and say "If quitting is even an option for you, then you should probably quit." But I'm not sure that's the best answer.

Just because you can't play in the NBA doesn't mean you shouldn't play basketball. As a writer, you have to ask yourself some questions: --Do I enjoy writing? If the answer is a BIG FAT NO, then that might indicate to pursue something else. However, if the answer is YES, then continue on. --What are my goals as a writer? Are they realistic? Just as someone who started jogging will not qualify for the Olympics, writing one screenplay won't have Spielberg knocking down your door. --How can I improve as a writer? Keep learning. As Scott says... Read Scripts. Watch Movies. Write Screenplays. If you like writing, keep writing. This is a marathon -- not a sprint.

The hardest thing for a screenwriter is for him or her to know when their stuff is good, particularly when you're trying to break in and have no experience. Even Bill Goldman has people read his stuff. I chose competitions, because they give me the opinion of someone (actually more than one person) who has no stake in my psychic well being. Sometimes that opinion is nonsensical, but more often than not I get sage advice, which I act on. Also, I make sure not to get too down on negative criticism, nor too up on positive comments. Other methods may work for you.

I've noticed that good writers are often very insecure, whereas mediocre ones are full of self-confidence. I think it's because a writer must be quite sensitive, even a little bit emotional, for their work to provide insight into the human condition; this is what makes them constantly question themselves. Mediocre writers can just bulldoze ahead without thinking about it too much, and perhaps this is why so many of them seem to "make it". I think that once you've produced something that people (not just your family) tell you has affected them in some way, then you can assume that you have talent. Not only do you need good ideas, but you need the moxie to follow them through to completion in order to have talent.