knowing what you know does not lessen your knowing the same thing. That fact is a given in the world, and it makes intellectual property different. Unlike apples, and unlike houses, once shared, ideas are something I can take from you without diminishing what you have.
It does not follow, however, that there is no need for property rights over expressions or inventions.[30] Just because you can have what I have without lessening what I have does not mean that the state has no reason to create rights over ideas, or over the expression of ideas.
If a novelist cannot stop you from copying (rather than buying) her book, then she may have very little incentive to produce more books. She may have as much as she had before you took the work she produced, but if you take it without paying, she has no monetary incentive to produce more.
Now, of course, the incentives an author faces are quite complex, and it is not possible to make simple generalizations.[31] But generalizations do not have to be perfect to make a point: Even if some authors write for free, it is still the case that the law needs some intellectual property rights. If the law did not protect authorship at all, there would be fewer authors. The law has a reason to protect the rights of authors, at least insofar as doing so gives them an incentive to produce. With ordinary property, the law must both create an incentive to produce and protect the right of possession; with intellectual property, the law need only create the incentive to produce.
This is the difference between these two very different kinds of property, and this difference fundamentally affects the nature of intellectual property law. While we protect real and personal property to protect the owner from harm and give the owner an incentive, we protect intellectual property to ensure that we create a sufficient incentive to produce it. “Sufficient incentive,” however, is something less than “perfect control.” And in turn we can say that the ideal protections of intellectual property law are something less than the ideal protections for ordinary or real property.
This difference between the nature of intellectual property and ordinary property was recognized by our Constitution, which in article I, section 8, clause 8, gives Congress the power “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.”
Note the special structure of this clause. First, it sets forth the precise reason for the power—to promote the progress of science and useful arts. It is for those reasons, and those reasons only, that Congress may grant an exclusive right. And second, note the special temporality of this right: “for limited Times.” The Constitution does not allow Congress to grant authors and inventors permanent exclusive rights to their writings and discoveries, only
