Epicurus’ Scientific Method and Cosmology

Emre Keskin

University of South Florida

In contrast to Aristotelian cosmology, Epicurean cosmology maintains that the universe is infinite. Yet, the infinity of space comes with a cost. Epicureans had to introduce boundaries between ‘the worlds’ that make up the universe. As Furley indicates, ‘what they saw in the night sky was not the beginning of the infinite universe: it was rather the boundary beyond which the infinite universe began’ (‘Infinite Universe’, 572). This meant that Epicureans had to concede that the observable universe was indeed finite and there were many causally isolated and unobservable finite worlds, whose aggregate constituted the infinite universe. Therefore, central elements of the Epicurean cosmology were thought to depend on guesswork rather than scientific inquiry. Developments in modern cosmology, however, have shown that according to certain models, the universe operates in a manner similar to Epicurean cosmology. Particularly, the eternal inflation model argues that there are causally isolated worlds that make up the universe. In this paper, I restructure the theory of the infinite universe as presented by the Epicureans in a way that is impervious to the charges of guesswork. I argue that Epicurean appeal to unobservable parts of the universe was a not a choice; it was an unavoidable physical consequence of constructing a theory of infinite space whose foundations depended on atomism and Epicurus’s scientific method. Of course, a proper understanding of Epicurus’s scientific methodology is essential for this project. I argue that for Epicurus in the larger scope the theory is more important than isolated observations. Although he accepts the possibility of multiple explanations of physical phenomena within a particular world, he could not accept the possibility of multiple explanations of foundations of the cosmos. The outcome is an asymmetry in the direction of inferences in Epicurus’s scientific method. Bailey (1964), however, fails to notice the asymmetry of inference. He argues that Epicurus’s methodology regarding both the atomism and the explanations of heavenly phenomena is the same. He, then, tells us that there is no principled way to answer why Epicurus does not allow a different explanation instead of atomism while he accepts possibility of different explanations of the causes of heavenly phenomena. In contrast to Bailey’s interpretation, the correct way to understand Epicurus’s scientific method depends on appreciating the asymmetry between the approach to foundational issues and possibility of different explanations of non-foundational issues that depend on the unique foundations. Given this proper understanding of Epicurus’ scientific methodology, his solution was the only proper explanation of the structure of the universe that fit both the observations of heavenly phenomena and the constraints of the scientific inquiry. Although I take cues from modern physics to vindicate the Epicurean ideas of space, the restructuring of Epicurean cosmology does not require appealing to modern cosmology to show the necessity of using infinity to explain the physical nature of space. In other words, from within the confines of the physics available to the Epicureans, it is possible to show that their concept of infinite space is defendable against the charges of depending on guesswork.