Many researchers have argued that evolutionary developmental biology (evo-devo) constitutes a challenge to standard evolutionary theory, requiring the explicit inclusion of developmental processes that generate variation and attention to organismal form (rather than adaptive function). An analysis of these developmental-form challenges indicates that the primary concern is not the inclusion of specific content but the epistemic organization or structure of evolutionary theory. Proponents of developmental-form challenges favor moving their considerations to a more central location in evolutionary theorizing, in part because of a commitment to the value of mechanistic explanation. This chapter argues there are multiple legitimate structures for evolutionary theory, instead of a single, overarching or canonical organization, and different theory presentations can be understood as idealizations that serve different investigative and explanatory goals in evolutionary inquiry.