_The Usefulness of a Temporary Monopoly of a New Device for Production._--If an invention became public property the moment that it was made, there would be small profit accruing to any one from the use of it and smaller ones from making it. Why should one _entrepreneur_ incur the cost and the risk of experimenting with a new machine if another can look on, ascertain whether the device works well or not, and duplicate it if it is successful? Under such conditions the man who watches others, avoids their losses, and shares their gains is the one who makes money; and the system which gave a man no control over the use of his inventions would result in a rivalry in waiting for others rather than an effort to distance others in originating improvements. This fact affords a justification for one variety of monopoly. The inventor in any civilized state is given an exclusive right to make and sell an economical appliance for a term of years that is long enough to pay him for perfecting it and to pay others for introducing it. Patents stimulate improvement, and the general practice of the nations indicates their recognition of this fact. They all give to the inventor a temporary monopoly of the new appliance he devises, but this monopoly differs from others in this essential fact: the man is allowed to have an exclusive control of something which otherwise might not and often would not have come into existence at all. If it would not,--if the patented article is something which society without a patent system would not have secured at all,--the inventor's monopoly hurts nobody. It is as though in some magical way he had caused springs of water to flow in the desert or loam to cover barren mountains or fertile islands to rise from the bottom of the sea. His gains consist in something which no one loses, even while he enjoys them, and at the expiration of his patent they are diffused freely throughout society. _Possible Abuses of the Patent System._--It is of course true that a patent may often be granted for something that would have been invented in any case, and patents which are granted are sometimes made too broad, and so cover a large number of appliances for accomplishing the same thing. In these cases the public is somewhat the loser; but for the reasons about to be given this loss is far more than offset by the gain which the system of patents brings with it.