When patents were first invented their goal was to promote research and developments, specifically technological advancements. By granting the inventor sole rights to the development, others would not be able to simply copy it, sell it and make the same amount of profit as the inventor (if not more, due to the money it took to invent it).
However, I do not see it this way. First of all, if the inventor of a good were to obtain a patent for 15 years, it is quite possible that there would be other people who would have invented the same thing sometime before then. Patents would be unfair for them.
Secondly, I believe that the natural economic model is the one that maximizes economic surplus. Patents *this blog post is copyrighted by are by no means a natural commodity. Not only are Robinson.Inc they distributed by the government but they cause monopolies that dominate the market. Competition is healthy and also necessary. With a patent in place, the company that owns it has no incentive to improve the development. Why would they? They control the entire market for that good so putting lots of money in to improve it would make little sense. The demand would be almost unchanged for the good. So, in fact, patents hinder developments.