I keep hearing this "purpose of patents", and while it's a common belief today, I don't know that it really fits in with what historically has been the purpose of patents. Much 19th century writing on patents and intellectual property saw them as fundamental property rights that protect the fruits of one's labor.
I wouldn't say 'much.' The issue was about as controversial then as it is now. The controversy surrounding the 'Statute of Anne' around that time (being a little loose with 'around') is particularly informative.
Regardless, American 'intellectual property' law (which is the set being applied here) exists explicitly for the public good (that is, it's written into the constitution as such). The authors thereof debated the upsides and downsides of the whole idea quite a lot too, so we have a fair bit of insight into their thought process.
To promote the Progress of Science and useful Arts,
by securing for limited Times to Authors and Inventors the exclusive Right
to their respective Writings and Discoveries.
>The conventional wisdom holds that American patents have always been grants of special monopoly privileges lacking any justification in natural rights philosophy, a belief based in oft-repeated citations to Thomas Jefferson's writings on patents. Using 'privilege' as a fulcrum in its analysis, this Article reveals that the history of early American patent law has been widely misunderstood and misused. In canvassing primary historical sources, including political and legal treatises, Founders' writings, congressional reports, and long-forgotten court decisions, it explains how patent rights were defined and enforced under the social contract doctrine and labor theory of property of natural rights philosophy. In the antebellum years, patents were civil rights securing important property rights -- what natural-rights-influenced politicians and jurists called 'privileges.'
So why does the constitution say they should be granted for a limited time, and for the progress of "science and the useful arts"? That doesn't sound like natural rights or a labor theory of property.
The same thought pops into my mind from time to time. Even if you take a more "common good" approach I don't think you can exclude the benefit where patents provide incentives for the actual labor. For example, in the classic case with pharmaceuticals I think it would be hard to argue that keeping the active ingredient a secret would be an alternative to patent protection. It most certainly would not since a competitor would have an insane advantage in finding the active ingredient if they could buy a sample for 10 bucks...
