Do patents encourage innovation?

It is often said that without patents pharmaceutical companies would no longer be able to introduce new drugs and that without copyright books would no longer be published, music no longer broadcast and films no longer made. Is it true, then, that with weaker intellectual property rights and greater freedom to copy others, technological progress and artistic creativity would suffer? No, it is not self-evident that this is the case. Indeed, it is very likely that the opposite is true.