For instance, if a certain individual owns the idea for airplanes, there are always ideas for gliders, helicopters, and devices yet unknown for other individuals to own. On the other hand, each idea is unique, so the taking of any idea as private property leaves none of that idea for others (Locke, 1690, Chap. V, Sect. 27). The first perspective would assert that there are always other ideas, while the second perspective would assert that ideas build upon each other, and that just because ideas are similar in one respect does not mean they are similar in other respects. Under the first perspective, the taking of intelle ctual property passes the Lockean Proviso, and under the second perspective, it fails.