The sixteenth-century physician and philosopher Julius Caesar Scaliger suggests that in particular cases plants can come into being that belong to a plant species that did not exist before. At the same time, he holds that God could not have created a more perfect world. However, does the occurrence of new species not imply that the world was not the best possible world from the beginning? In this article, I explore a set of metaphysical ideas that could provide Scaliger with the means of solving this problem: (1) His version of the notion of a plurality of substantial forms in every living being, and (2) his version of the notion of the ordained divine power. As it turns out, Scaliger analyzes the generation of new species in terms of a development of subordinate substantial forms into dominant substantial forms. Thereby, previously existing essences of plant parts become essences of plants. These plants, thus, possess essences that no previously existing plant possessed and, in this sense, belong to a new species. In this way, Scaliger avoids positing the occurrence of new essences, thus saving the best possible world thesis. Moreover, he believes that all substantial forms stand in a relationship of mutual existential dependence by means of which God safeguards the persistence and unity of the world. This is why the agency of subordinate forms turned dominant can be understood as an expression of the ordained power of God.