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CHAPTER TWO

THE ACTIVE PRINCIPLE IN STOIC PHILOSOPHY

Håvard Løkke

Introduction

Unlike the contemporary Epicureans, the ancient Stoics believed that there exists an active principle that governs the in accordance with a rational plan. Th is is, in our parlance, a metaphysical belief. But whereas ’s works aft er the Hellenistic era were edited in such a way that a part of his philosophy came to be called , this did not happen to the Stoics. So in order to get as clear as we can on the Stoics’ views and arguments on the active principle, we must turn to the part of their philosophy called physics. Th e Stoics divided philosophical inquiry into three parts. In addition to physics, there was one part dealing with ethics and another with logic. All Stoics agreed that these parts are closely related. But there was some disagreement as to what the relations are. Some Stoics said that if philosophy were a garden, physics would be its trees, ethics its fruits, and logic its surrounding wall; others said that if philosophy were an egg, physics would be its yolk, ethics its white, and logic its shell.1 Whatever we make of these analogies, it is clear that physics is a central subject in Stoic philosophy. But it should also be clear that most of the Stoics did not study physics for its own sake alone; at least (ca. 280–205 BC), the third school-arch of the Stoa, held that one should not approach Stoic ethics without having fi rst heard at least the main points in Stoic physics.2 Further, all Stoics agreed that physics is itself subdivided. But again there was some disagreement as to what the subparts are. On one view, physics is made up of fi ve topics: “On bodies”, “On principles”, “On elements”, “On ”, and “On limits, place, and void”; on a diff erent

1 Diogenes Laertius, of Eminent Philosophers 7.39–40; LS 26B. 2 Plutarch, On Stoic Self-Contradictions 1035b–d. 50 håvard løkke view, it consists of three subparts: “On the cosmos”, “On the elements”, and “Th e inquiry into causes”.3 Whatever we make of this disagreement, it is clear that four notions are of key importance in Stoics physics: body, principle, element, and causation. My discussion in this paper is focused on these four notions—plus one that does not make up a separate topic, namely the notion of . Pneuma is a physical stuff that is made up of the elements fi re and ; on the Stoic view, it is the vehicle of the active principle, the that governs the cosmos and with which we human beings ought to govern our lives. As is well known, our evidence for early Stoic philosophy is quite poor. Th ere is in fact a lot of material bearing on nearly all parts of Stoic philosophy, but the main problem is that much of this material is made up by polemical attacks from hostile adversaries and hence only indirect testimony, at best. Having said that, our evidence for Stoic physics is relatively good, and maybe better than our evidence for any other part of their philosophy except ethics. Th is is mainly because we are so fortunate as to have two complete (or nearly complete) ancient texts bearing on the issue. One is Seneca’s Natural Questions, written, it seems, in 62–65 AD. Th e other text is a book on astronomy, now known as Th e Heavens, written by a Stoic called , prob- ably mid-second century AD.4 Th ere is also much useful information about Stoic physics in ancient doxographers, like Diogenes Laertius and Johannes Stobaeus. So we have enough evidence to piece together a picture of the Stoics’ views and arguments on the active principle. Yet, it is only fair to add that the access we now have to Stoic physics is limited; it is as if we had to piece together Aristotle’s physics from his Meteorology and a few isolated doctrinal reports, without having either the Physics or the De anima. Here is how I proceed in trying to create as comprehensive a picture as possible. First I briefl y sketch the historical background and con- text out of which I believe the Stoic position arose. Th en I look at the notion of body, which the Stoics seem to regard as the pivotal one in their theory. Th is leads to a discussion of that into which body can be analyzed, i.e. the active and the passive principle, and that out of which a body is made up, i.e. the four elements. And this in turn leads to a discussion of pneuma, the bodily vehicle of the active principle, which

3 Diogenes Laertius, Lives of Eminent Philosophers 7.132; LS 43B. 4 See Cleomedes’ Lectures on Astronomy.