 Understanding the concept religion in this polythetic way produces a graded hierarchy of  instances.[9]  A form of life that has all five of these characteristics would be a prototypical example of a religion. Historically speaking, prototypical examples of the concept are likely to be instances to which the concept was first applied. Psychologically speaking, they are also likely to be the example that comes to mind first to those who use the concept. For instance, robins and finches are prototypical examples of a bird, and when one is prompted to name a bird, people are more likely to name a robin or a finch than an ostrich or a penguin. A form of life that has only four of these characteristics would nevertheless still be a clear example of a  religion.[10]  If a form of life has only three, then it would be a borderline example. A form of life that has only two of these characteristics would not be included in the category, though such cases might be considered “quasi-religions” and they might be the most interesting social forms to compare to religions (J. E. Smith 1994). A form of life that only had one of the five characteristics would be unremarkable. The forms of life that had three, four, or five of these characteristics would not be an unrelated set but rather a “family” with multiple shared features, but no one characteristic (not even belief in superempirical beings or powers) possessed by all of them. On this polythetic approach, the concept religion has no essence, and a member of this family that only lacked one of the five characteristics—no matter which one—would still clearly be a  religion.[11]  As Benson Saler (1993) points out, one can use this non-essentialist approach not only for the concept religion but also for the elements within a religion (sacrifice, scripture, and so on) and to individual religions (Christianity, Hinduism, and so on).