The article examines the place of the animal world in the picture of the world by Philostorgius. Being a prominent representative of the Alexandrian school and the heretical church historiography of the IV-V cent. AD, he approached this issue much more seriously, paying attention to the symbolism due to the appearance and relationship of a person with one or another biological species. All this correlates with the methods of biological descriptions in antiquity, some of which are also used by modern biologists. Careful handling of the biological terminology of Aristotle and Pliny is noticeable in the use of such a key concept of the Philostorgian worldview as φύσις.Regarding animals, he uses this word in the sense of gender, which successfully correlates with Aristotle's “History of Animals”. It is concluded that the descriptions of animals in the “Ecclesiastical History” is an imitation of “Natural History” by Pliny the Elder and “History of Animals” by Aristotle. Trying to follow, on the one hand, Polybius in covering the political events of the Roman Empire; on the other hand, Eusebius of Caesarea in a story about the religious struggle between currents in Christianity, Judaism and pagan cults; Aristotle and Pliny the Elder, in an effort to represent the entire cosmos from Paradise and heaven, to the depths of the earth and Hell, Philostorgius created a religious and political work with elements of scientific descriptions, intended for an educated reader and aiming to educate a citizen of Rome, a diversified Eunomian.