For reference the definition is, "an unpredictable or unforeseen event, typically one with extreme consequences." Let's take truly great works of art as an analog to black swans. I agree you cannot create a formula for churning out more great art, as one struck in a certain direction reduces the greatness and significance of others in that direction. But if some wealthy patron collected a bulk of the worlds great artists, giving them creative freedom, tools and space... I cannot say for sure it would result in more "great art" than would be produced otherwise. But I would not say it's impossible by definition, as you do.