Norms or Types just as nature is ever thrifty of motifs even in her endless abundance, constantly repeating her basic forms, but modifying them a thousand different ways according to the condition of her creatures and their mode of life, stretching or curtailing some, hiding or revealing others— just as nature has her evolutionary processes, within whose limits old motifs continually reappear in new creations. Nothing, therefore is purely arbitrary, but all is governed by circumstance and relationship.