I have written a decent amount about the concept of nonrival consumption. It is the economic characteristic that distinguishes public goods from private goods. Ideas are nonrivalrously consumed because the marginal cost of allowing another person to access and consume the idea is zero. Sure, the costs of distributing ideas and explaining them may be positive, but it costs nothing to allow another person to consume an idea because ideas do not deplete – - that is, if you consume the idea, there is no less of it for me. (Jefferson wrote a famous paragraph on this that people like to quote.) Apples, on the other hand, are another story.
Now some disagree with the notion that ideas are nonrival, and I have always been puzzled by this. Typically, they conflate consumption and distribution or something like that. But here is a somewhat different approach; it occurred to me that maybe what they are doing is focusing on the value generated by the idea. If we focus on the value or surplus generated by the production of an idea, that value is finite (even if potentially dispersed across many people and well into the future) and thus rivalrously consumed. If you get some chunk of the value, then I cannot get that same chunk. Then, if we allow everyone to access that value without restriction – - e.g., as direct consumers or as competitors seeking to appropriate some value by using the idea to sell products or services to consumers, viola, a tragedy of the commons?
Well, no. Because the value itself is depletable no matter what; it is not a sustainable, renewable resource (unlike the idea, which is sustainable and nondepletable). Overconsumption is not the risk with which we are concerned.
I have more to say on this, and will be doing so in some essays and perhaps on the blog, but let me see if this sparks some comments…