 This situation threatens Ariew’s suggestion that canalization might serve as a unifying concept in biology and psychology. In order to effectively unify disparate phenomena, such as the development of song in different species of birds, a concept must provide some relatively simple organizing framework. Ariew painted a simplistic picture of birdsong, giving the impression that different species could be arranged along a single environmental axis. Griffiths and Machery object that there are indefinitely many environmental axes along which a group of species might be compared. Moreover, the arrangement of species as more or less canalized will vary from one environmental axis to the next. Such complexity and lack of coherence makes canalization a bad candidate for conceptual unification.