It has been argued that Greek natural philosophy began when philosophers rejected religious explanations for natural phenomena, favoring physical explanations instead. This early science was not marked by this bold rejection, though, because it developed gradually from other Greek philosophical traditions, which frequently included theological elements. Even the philosophers who most influenced the later development of science, Plato and Aristotle, referred to gods in their natural philosophies. Their works were in many ways less theological than those of their predecessors, but they nonetheless never declared theology to be a separate enterprise from natural science. Instead, these philosophers tried to understand all that they could about the world, unconstrained by modern concepts about the purely empirical nature of science and modern distinctions between intellectual occupations. They thus wrote about mathematics, theology, political theory, biology, psychology, ethics, and a range of other topics without regard to the boundaries that have since developed between these disciplines.
These subjects do not all intermingle in Greek philosophy chaotically, though; instead, certain subjects tend to relate to each other. A dialogue like Plato’s Republic that focuses on an ethical question—what is justice?—delves also into political theory, and the easy juxtaposition of these subjects suggests that they are closely related. Similarly, works like Plato’s Timaeus and Aristotle’s Metaphysics focus on natural philosophy but also refer to gods, suggesting a relationship between the science and theology of their time. In both of these works, the gods or other eternal, uncreated beings are used to explain phenomena, but are not used to explain all phenomena. Some things have purely naturalistic explanations, but the first, most grand, and most complex phenomena are the works of the divine.
The relationship between natural philosophy and theology was a dynamic one, though, and earlier philosophers often focused more on theology than did Plato and Aristotle. Empedocles, who Aristotle credits with claiming that all is made of four elements, also wrote about Aphrodite and Zeus. Many philosophers described the vastness of the infinite, and, according to Theophrastus, Anaximander was the first to claim “that the material cause and first element of things was the Infinite.” This emphasis on the infinite is one that is common within theology to this day, and Anaximander’s statement about the source of matter sounds more like modern religion than modern science.
Plato and Aristotle
Later Greek philosophy, particularly that of Aristotle, is sometimes more empirical, but even in the rationalist works of Plato there is less reliance on gods than in pre-Socratic natural philosophy. The references that exist to gods are prominent, though, and often suggest a strong link between science and religion. Near the beginning of Timaeus, for instance, Plato makes an important statement about the uncertain nature of the sciences, but includes theology among them. “We won’t be able to produce accounts,” he writes, “on a great many subjects—on gods or the coming to be of the universe—that are completely and perfectly consistent and accurate.” The uncertainty of science has been claimed by many scientists and philosophers as one of its defining characteristics, but if it is uncertainty and imperfect accuracy that distinguish science from religion, Plato claims, theology is as much a science as cosmology.
And yet, in part because it was so influential, Plato’s conception of the supreme deity is not all that different from modern Western religious conceptions. The role of the divine that has best endured in Western thought is that of creator, and both Plato and Aristotle claimed that a god created the universe. They did have different views of this creation, though. Plato attributed the creation of the universe to the Demiurge, the “maker and father of the universe” who, following Plato’s doctrine of forms, formed the universe based on “the eternal model.” This being, who Plato sometimes referred to as a god, “was good” and “wanted everything to be good.” It found the natural materials of the universe in chaos, and “the first thing the god then did was to give them their distinctive shapes, using forms and numbers.” The Demiurge is thus credited with creating the four elements—earth, air, fire, and water—“to be as perfect and excellent as possible, when they were not so before.” Furthermore, though Plato describes the structures of these elements in detail, he admits that “principles yet more ultimate than these are known only to the god, and to any man he may hold dear.”
Aristotle also formulated a theology-dependent natural philosophy. The best known theological element of Aristotle’s worldview is the Prime Mover, which historian of science David C. Lindberg describes as “a living deity representing the highest good, wholly actualized, totally absorbed in self-contemplation, nonspatial, separated from the spheres it moves.” This deity, or actually these deities, as Aristotle concludes that there is one for each celestial sphere, are the final causes of the motion of the spheres, the reasons that the planets move.
The nature of theology
Aristotle’s theology had other elements too, though. One of these is part of his epistemology, which is introduced in Metaphysics and tightly coupled with his natural philosophy. In Metaphysics, Aristotle determines that “the science which knows to what end each thing must be done is the most authoritative of the sciences.” This science is that which “deals with divine objects,” theology. It is more than this, though. Theology to Aristotle is not only the science of the divine; it is “a divine science,” as it is that which God knows. “God,” wrote Aristotle, “is thought to be among the causes of all things and to be a first principle, and such a science either God alone can have, or God above all others.” Because he has determined that “the divine power cannot be jealous,” the latter must be the case, and theology must be a science accessible to humans but mastered only by God. Aristotle does sense that theology is perhaps more logical and less empirical than other sciences, but it is still clearly a science, as it aims to understand “in order to escape from ignorance.” Furthermore, Aristotle asserts, because this is its only goal, theology is the best and least necessary (or perhaps least practical) science.
Plato, Aristotle, and earlier philosophers share the conclusion that understanding the one or more gods they believed in is part of understanding the world. The idea that science began when philosophers tried to explain nature without recourse to the supernatural does have some truth to it, but this change in method of explanation did not happen suddenly in ancient Greece. On the contrary, for most of the history of science philosophers and scientists have used both natural and supernatural explanations for phenomena. A late example is William Paley’s 1802 Natural Theology, which drew from both science and religion to present a theory of biology. It has only been during the modern era that scientists have made a conscious effort to constrain their theories to the observable world and that science and religion have become, in Stephen Jay Gould’s phrase, “non-overlapping magisteria.” The greatest of the ancient Greek natural philosophers may have explained most phenomena naturally, but they also each referred to divine causes when they thought them to be the best explanations.