An Essay on the Unity of Stoic Philosophy, first published in 1962, has been republished, with a new foreword and an appended essay that discusses Stoic political philosophy.1 Christensen argues that Stoic philosophy was a unified and well-structured whole. His examination comprises four chapters, the first concerning Stoic ontology, and the remaining three following the traditional tripartite division: physics, dialectic, and ethics. Additional appendices provide reflections on method, notes and references, and a list of technical terms.2 As documented in the foreword written by Sten Ebbesen and Troels Engberg-Pedersen, former students of the author, the book received a mixed assessment on publication, and made no great impact.3 Ebbesen and Engberg-Pedersen argue that the time is right for a re- appraisal of Christensen’s concise interpretation of Stoicism as a coherent and sophisticated philosophical theory. Christensen’s study is engaging, sometimes challenging, and is certainly worth reading.
Christensen claims that he is most able to make sense of the diverse passages that constitute our evidence of Stoic doctrine by identifying the fundamental beliefs and basic schema of the Stoic world-view. He identifies two central Stoic commitments: ‘(1) They fervently believe that there exists a world order; (2) Reality is not “really” something in principle beyond our experience, it is, as we are directly aware of it, a subtle, shifting, never-ceasing flow of change, of matter in motion’ (p. 14). A theme of Christensen’s book is that the Stoics developed their metaphysical views in part as a response to Aristotelianism, which would have provided the most comprehensive store of metaphysical concepts at the time when members of the Stoa were philosophizing. A notable feature of Christensen’s analysis of Stoicism is that the Stoic Sage is very much set apart from the common stock of humankind: the Sage knows everything, and is in absolute and perfect conformity with the cosmos.
Christensen argues that Stoics maintain that reality is one single substance which can be conceived of as having two aspects, active structure working on passive matter. As a single body, the whole cosmos is the sole example of an Aristotelian concrete particular. This particular is also Aristotelian prime matter, since it is the substrate in which all changes occur, and it is the sole example of what Aristotle would identify as a Form, since the world is ‘a concretum constituted by all of matter characterised exhaustively by actual formal features’ (pp. 19-20). Thus, the Stoics claim that one and the same thing, the material body that is the cosmos, corresponds to each of Aristotle’s three possibilities for something’s qualifying as a substance.
With the cosmos as the only concrete particular, there can be no other genuine individual substances. Objects that appear to be substances are in fact best understood as fields subject to physical change. Aristotle identified four kinds of change (change of substance, quality, quantity, and place). Christensen argues that the Stoics recognize only the last of these four, i.e. change of place (p. 27). What convention calls an object is in fact a field within which there are various stable and balanced movements of matter: ‘What Aristotle usually would have conceived as substances are to the Stoics tensional fields. The world as a whole is such a tensional field, ordinary objects being, so to say, tensional sub-fields’ (p. 35). The stable motions of tensional fields differ in complexity relative to the type of object that the tensional field contains: stones and bones being simpler than souls, which are themselves simpler than rational souls.
Stoic dialectic provides the tools needed to analyse and understand the world. The Stoic schema of types of grammatical term (“name”, “intransitive verb”, etc.) corresponds to the ontological schema of genera (the qualified, the disposed, etc.). For example, by using a name we refer to some region as having an individual quality. The tensional field that is Socrates contains very complex and stable motions characteristic of a rational soul, and the name “Socrates” corresponds to the individual property of “being Socrates”, just as the grammatical class of names corresponds to the ontological class of individual quality [ἰδίως ποιόν]. Christensen treats the genera as reference classes. An object might to belong to every reference class, since the one object can be understood in different ways: ‘Socrates is an individual quale, but he is also, as everything else, prime matter in a certain state (ὕλη πως ἔχουσα)’ (p. 51).
Rational agents (i.e., ordinary human beings) experience the world and come to form beliefs about it. Some of these beliefs will be true. Over time an agent’s set of true beliefs expands and becomes richer and more complex, as the agent experiences the flux and change of the external world and gradually looks for patterns and stabilities, seeking to ensure that his set of beliefs is internally coherent and externally accurate (p. 58). The ultimate, ideal outcome of this process is that the agent comes to have knowledge, but this is possessed only by God and the Sage. The beliefs of imperfect rational agents count as opinion. Knowledge must be absolutely coherent and maximally comprehensive: ‘complete knowledge, in an idealist sense, is only possible for God or the Sage’ (p. 61).
The Sage lives virtuously, which means that he lives in agreement with nature. The Stoics claim that every living creature has an innate drive for self-preservation and the preservation of its constitution: this is the doctrine of oikeiosis, which Christensen translates as “adaptation”. The Sage’s process of adaptation finds him conforming to the universe as a whole: ‘ [The Sage] is, in a sense, God. He is really living consistently with himself and with Nature, having “knowledge of whatever happens by nature”, because he is Nature’ (p. 68). Only the actions of the Sage are virtuous, and in acting the Sage does not seek for anything external. The Sage represents the highest expression of the Stoic vision of unity with the cosmos.
Christensen discusses Stoic political philosophy in an appendix, and he argues that the Stoics were committed to social and political reform. He describes the ideal Stoic community as anarcho-syndicalist, but suggests that the Stoics recognized the viability of other constitutional forms, such as an enlightened monarchy.
Several of the interpretations of Stoic doctrine that Christensen offers are intriguing. The book is short but rich in argument, and I have here outlined only its most prominent claims. Christensen’s prose is mostly lucid, but occasionally dense. Once or twice (e.g. the discussion of Stoic physics in terms of fields) I would have liked the argument to proceed a little more slowly. The text does not overflow with footnotes, though it is clearly the product of careful consideration of many Stoic texts.
Nonetheless, I believe that there are several points at which Christensen’s argument is not viable, especially concerning the characterisation of the Sage’s actions and knowledge. Christensen suggests that the virtuous actions of the Sage do not aim at the acquisition of anything external: ‘For the virtuous man, moral action and the purpose or object of action coincide’ (p. 69). It is true that it makes no difference to an agent’s happiness whether or not he acquires any external. (This is at least true for any external that is an indifferent.) However, Cicero’s testimony concerning suicide seems to indicate that a virtuous action will have some external as its object.4 This is unsurprising, since a virtuous action is simply a proper action ( kathēkon) performed by a virtuous agent, and proper actions take externals as their objects.
I think Christensen is also incorrect (p. 72) to correlate valued objects and proper actions. Diogenes Laertius reports that whatever is promoted has worth, but he also reports that a proper action can aim at something which is demoted and has a lack-of-value ( apaxia).5 In the right circumstances, the Sage would maim himself, but self-harm is presumably demoted. Since the Sage’s actions are always proper, there are proper actions that aim at demoted indifferents.
Finally, Christensen argues that the Sage has comprehensive knowledge of the cosmos, since the objective content of the ideal account of Nature is identical to the Sage’s knowledge, understood as a well-ordered set of firmly-held beliefs (p. 69). However, if the Sage does know everything that can be known, this seems difficult to square with Stoic views about reservation, according to which the Sage encounters nothing unexpected and always acts with reservation.6 If the Sage knew everything then it is true that he would encounter nothing unexpected, but it is hard to see what acting with reservation might then amount to, or why any modification to the Sage’s actions would be needed.7
The Stoics presented their philosophy as a systematic account of the universe and the place of humankind within it. Christensen’s work is an sustained attempt to reconstruct Stoicism as a complete doctrine, and the author balances careful exegesis against necessary supposition in his treatment of the fragmentary evidence we have of Stoic views. Fifty years after it was first published, this re-issue allows us to appreciate Christensen’s scholarly efforts – or, to appreciate them once more.8
1. The book did not discuss Stoic political philosophy when it was first published. Christensen’s essay “Equality of Man and Stoic Social Thought” was first published in I. Kajanto (ed.), Equality and Inequality of Man in Ancient Thought (1984).
2. The appendix giving a habilitation summary in Danish has been removed for the republication.
3. Compare Phillip De Lacy’s highly critical review, in Gnomon 35 (1963), pp. 308-10, with the positive report from A. A. Long, Hellenistic Philosophy (1986; second edition), p. 254.
4. Cicero, De Finibus 3.61.
5. See DL 7.106, 109-10.
6. See e.g. SVF 3.564.
7. G. B. Kerferd discusses the possibility of the Sage’s being omniscient, referring to Christensen’s interpretation: ‘What Does the Wise Man Know?’ in J. M. Rist, ed., The Stoics (1978), pp. 125-36.
8. I am grateful to Tad Brennan and Liz Hobday for advice on this review.