Forget the abstract arguments about corporations being "encouraged" or whatever you think I think. Just tell me how it would work.
If it helps, imagine that you run a pharmaceutical firm, and you have the choice to spend hundreds of millions of dollars researching a drug which, once perfected by your researchers, is not owned in any sense (even temporarily) by you, but rather immediately becomes a generic commodity worth fractions of a cent per unit, and which cannot possibly earn you back the money you spent developing it. In that situation, would you start the research? And if not, where will the new drugs come from?