In many cases a significant portion of the potential value of a manufactured object arises from the idea(s) used to create the object, which are now embodied in it. The principal utility (value) of a book, for instance, typically lies in the ideas expressed in the book. Similarly, a newly invented machine may be especially valuable because it can be used as a prototype for other machines of the same kind. As previously observed, an idea need only be produced once, after which it is no longer a praxeological good or value for its creator, since he or she only needs one "unit" of the idea. In other words, the creator's actions are not affected by any necessity to produce more "units" of the idea or to avoid "depleting" it (p. 4.4:6). On the other hand, the idea may be a potential good (value) to others, who do not already have it in their "stock." The creator cannot literally bequeath an idea to others, since an individual can grasp an idea—whether on a superficial or a deeper level—only through a process of independent mental integration (cf. p. 2.4:4). The creator can, however, give or sell them a material representation, such as a book, a prototype, or an oral explanation, from which they can more readily reconstruct the idea with their own minds.