A good is joint, on the other hand, when consumption by one person does not diminish its availability to others. Intellectual goods, such as ideas, are not scarce in this sense, since one person's availing themselves of an idea does not, in itself, make it any harder for others to do likewise. The imposition of property rights, restricting access to goods, would appear much easier to justify in the case of non-joint goods than in the case of joint goods. After all, consumption of a non-joint good by one person means that other will be, in fact must be excluded from its consumption. A determination has to be made as to who will miss out, even if this determination is, as it were, the determination of fact, when one person does consume it, thereby preventing others from doing so.
Matters are rather different with joint goods, such as ideas.
This is true, for example of the vast amounts of information in public circulation. Nevertheless, it is not always true, since there are various forms of property rights over intellectual goods. The discussion above perhaps helps to show why this is. In a clear sense no-one is made worse off merely by the consumption of joint goods, so it is difficult to see that one is doing anything wrong in engaging in such consumption. But if I copy a video or a text, it is hard to see that anyone is worse off than if I had refrained from copying it, just in virtue of my copying it.