The Stoics on Ambiguity

The Stoics on Ambiguity R. BLAIR EDLOW IN SPITE OF A REVIVALof interest in the Stoic theory of language and logic that followed the publication of Benson Mates' Stoic Logic, 1 there has been no systematic study devoted to the ancient Stoic teaching on ambiguity (~t~tq~t~o~a). One major obstacle has been the scarcity of testimony in the extant tradition. Another has been textual corruption of the most informative doxographical account2 of the early Stoic (or Chrysippean) theory,a This last problem is overcome, however, by a long neglected 1903 dissertation4 containing an edition of Galen's De Captionibus, which includes this significant account. Much of my interpretation of the Stoic doctrine will be speculative. The documents that would provide a foundation for a more detailed study have not survived. Nevertheless , my hope is that by making this doctrine (based on present evidence) accessible to historians of philosophy and philosophers of language, some further ground may be gained in determining the nature of this Stoic teaching. The philosopher may be interested in studying ambiguity on both theoretical and practical grounds. On the one hand, theoretical reflection on ambiguity attempts to systematize and explain for its own sake this pervasive feature of language. Such work on ambiguity is justified simply by the increase in knowledge and insight it yields. On the other hand, there is considerable practical value in reflecting on the notion of ambiguity. It may aid the philosopher not only to recognize and avoid its occurrence in his own reasoning, but also to detect ambiguity in the discourse of others. Ambiguity, of course, is a main cause of argument invalidity.5 x Earlier in the century, Jan Lukasiewicz explored the Stoic theory of propositional logic in "Philosophische Bemerkungen zu mehrwertigen Systemen des Aussagenkalkuls," in Comptes Rendus des S~ances de la Socidtd des Sciences et des Lettres de Varsovie, XXIII (1930), Classe III, 51-77. 2 This text is most accessible to scholars as fragment 153 in H. von Arnim, ed., Stoicorum Veterum Fragmenta (Stuttgart: Teubner, 1964), II, 45--46 (hereafter SVF). Von Arnim's text is based on the C. G. Kiihn edition of De Captionibus penes Dictionem, in Galen, Opera Omnia, XIV (Leipzig, 1827), 582-598. a It is assumed here that the Stoic doctrine is wholly or at least primarily that of Chrysippus (c. 280-207 B.C.),who is reputed to have written seven treatises (in seventeen books) on the subject of ambiguity (dtp.tpt~o~ct).For the list of titles, SeeSVF II, #14 (which is the same as Diogenes Laertius, Vitae Philosophorum 7. 193). Von Arnim suggests that the entire discussion of the Stoic teaching that appears in Galen's De Captionibus is probably drawn from Chrysippus' "~e0~ ~qxtp~6o~.t~,"(SVF II, 46n.). 4 Carl Gabler, ed., Libellus de Captionibus quae per Dictionem Fiunt (Rostock, 1903). I am indebted to Professor Phillip DeLacy of the University of Pennsylvania who drew my attention to this work. William and Martha Kneale cursorily dismiss De Captionibus as a "little tract on fallacies" in The Development of Logic (Oxford: Clarendon Press, 1962), p. 182; and C. L. Hamblin in Fallacies, University Paperbacks (London: Methuen, 1972), p. 98, in a footnote, without argument questions the status of De Captionibus as a genuine work of Galen. 5 A famous example of a fallacy arising from ambiguity appears in J. S. Mill, Utilitarianism, ed. by O. Piest, 2nd rev. ed. (New York: Library of Liberal Arts Press, 1957), p. 44: "The only [423] 424 HISTORY OF PHILOSOPHY The study of ambiguity for the Stoics falls under the heading of Logic,6 one of their three divisions of philosophy (along with Ethics and Physics).7 The Stoics' interest in ambiguity, I will argue, is motivated at least in part by their concern to expose and explain certain fallacies, those caused by either an ambiguous premise or conclusion. Discussing ambiguity and fallacy in the same treatise is a common practice in antiquity: Aristotle treats ambiguity in the context of his work on fallacy in Sophistici Elenchi,8 and Galen (although writing nearly four centuries after the Stoics) theorizes about ambiguity in his book on fallacy (De Captionibus). As...