I agree that, without copyright, lots of creative works would (and did!) still get created. But there are certainly some creative works that only would get created if copyright law exists. Think of a Pixar-level animated movie or Hollywood-style live action movie, that involve huge teams of people working full time for extended periods.
[Edit: just be clear, people working on side projects on their own and huge multimillion dollar projects are two extremes of a large spectrum. I chose the opposite extreme to make a point but almost everything in the middle also only exists because of copyright.]
Maybe some would still exist to some level through alternative mechanisms e.g. government or charitable funding, or a group effort akin to open source. But I think it's clear that you're talking orders of magnitude less output.
Don't forget copyright also applies to software. It's even more clear that open-source movements work for software! But it's still the case that without copyright there would be some software that wouldn't get written. Certainly, speaking personally, my software economic output would be lower if it weren't my full time job!
[Edit: just be clear, people working on side projects on their own and huge multimillion dollar projects are two extremes of a large spectrum. I chose the opposite extreme to make a point but almost everything in the middle also only exists because of copyright.]
Maybe some would still exist to some level through alternative mechanisms e.g. government or charitable funding, or a group effort akin to open source. But I think it's clear that you're talking orders of magnitude less output.
Don't forget copyright also applies to software. It's even more clear that open-source movements work for software! But it's still the case that without copyright there would be some software that wouldn't get written. Certainly, speaking personally, my software economic output would be lower if it weren't my full time job!