1. Metaphysical roots
According to a well-known theory of Arthur O. Lovejoy, the idea of a scala naturae, a great chain of being, literally a “ladder of nature,” according to which all beings constitute a hierarchical sequence based on their degree of perfection, dominated natural philosophy and natural history until well into the 18th century. According to Lovejoy, this idea was rooted in three metaphysical principles: the principle of fullness, which holds t…