Few ideas in biology are regarded as more representing the state of the world than "species", and yet the original motivations for developing the notion in the 17th century were religious, in the work of Athanasius Kircher (c1602–1680), the Jesuit polymath. Prior to him, the use of the word "species" was interchangeable with "genus" in natural history. In order to accommodate all the "kinds" (species) of quadrupeds and birds on the Ark, in his tractate De Arca Noë, Kircher used several strategies, including eliminating those species that spontaneously generated (worms, insects and spiders), and those which were formed from hybridisation (such as giraffes, hyenas and several fabulous creatures).
Kircher stands at the cusp of modern natural history evolving out of the bestiary tradition, and De Arca Noë was a serious attempt at natural history within the confines of his set problem, with many woodcuts of the organisms concerned. His work informed Bishop John Wilkins, the English polymath, as he constructed a classification of all possible concepts, and to this end he employed John Ray to draw up the lists of species in his Essay toward a real character and a philosophical language as part of the Universal Language Project. Ray was chided by his colleagues, and so he commenced an empirical list of species, in the course of which he presented the first truly biological conception of the term.
I will then cover the subsequent history of the idea through to the Enlightenment, including the question of whether or not species were real or mere constructs of human thought.