The International Journal The International Journal of the of the Platonic Tradition 12 (2018) 111-131 Platonic Tradition brill.com/jpt Mathematics, Mental Imagery, and Ontology: A New Interpretation of the Divided Line Miriam Byrd* University of Texas at Arlington [email protected]; [email protected] Abstract This paper presents a new interpretation of the objects of dianoia in Plato’s divided line, contending that they are mental images of the Forms hypothesized by the diano- etic reasoner. The paper is divided into two parts. A survey of the contemporary debate over the identity of the objects of dianoia yields three criteria a successful interpreta- tion should meet. Then, it is argued that the mental images interpretation, in addition to proving consistent with key passages in the middle books of the Republic, better meets those criteria than do any of the three main positions. Keywords Plato − Republic − dianoia − hypothesis − mathematics In Book 6 of Plato’s Republic, Socrates uses the image of the Divided Line to dis- tinguish four mental conditions, two associated with the visible realm and two with the intelligible. He differentiates the subsections of the visible segment of the line, eikasia and pistis, by the objects grasped by the soul in each. However, when he marks the distinction between dianoia and noêsis, the conditions associated with the intelligible segment, he contrasts them based upon their methods of inquiry. Socrates tells us that dialectic, the epistemological method of noêsis, directly grasps the Forms, but he makes no mention of a unique class * I presented a version of this paper at the 2017 meeting of the ISNS in Olomouc and would like to thank conference participants for their helpful comments during discussion. © koninklijke brill nv, leiden, 2018 | doi:10.1163/18725473-12341411Downloaded from Brill.com10/01/2021 12:37:40PM via free access 112 Byrd of objects associated with dianoetic reasoning, a methodology he associates with mathematics. Consequently, there has been a history of controversy with- in Plato scholarship over the identity of the objects of dianoia, particularly the objects of mathematics, with disagreement as to whether Plato intended them to be intermediates as described by Aristotle, Forms, or sensible things used as images of the Forms. This debate has brought to light serious problems with accepting any of the major positions. After surveying the main arguments of the contemporary de- bate and presenting compelling arguments against each, I shall propose a new alternative. Agreeing with proponents of the intermediates that the mathema- ticians grasp intelligible entities that are not Forms, I shall argue, along with supporters of the sensible things interpretation, that the objects of dianoia share the same ontological level as the objects of pistis, thus avoiding adding an ontological level Plato never explicitly endorsed. 1 Contemporary Debate Concerning Objects of Dianoia There is a long tradition of interpreting the objects of dianoia as ontological intermediates.1 This position relies heavily upon Aristotle’s testimony, for in Metaphysics 987b14-18 and 1028b18-21 he directly attributes a theory of inter- mediates (τὰ μεταξύ) to Plato.2 According to Aristotle, Plato believed that the mathematicals (τὰ μαθηεματικά) existed at an ontological level between the Forms and the sensible things. Describing Plato’s view, Aristotle writes: Further, apart from both the perceptibles and the Forms are the objects of mathematics, he says, which are intermediate between them, differing from the perceptible ones in being eternal and immovable, and from the Forms in that there are many similar ones, whereas the Form itself in each case is one only. (987b14-18)3 1 This tradition may be traced back to Proclus, In Eucl. See particularly 4.14-5.10 and 10.16-11.25. More recent scholars holding this view include J. Adam (1902) 159-163; H.S. Arsen (2012); J.A. Brentlinger (1963); M. Burnyeat (1987) and (2000); 33-37; M.J. Cresswell (2012) 302-305; W.F.R. Hardie (1936) 49-65; M. Miller (2007) 319; D. Sedley (2007); and A. Wedberg (1955). 2 For other mention of intermediates, see 987b29, 991a4, 991b29, 992b16, 995b15-18, 997a35- b3, 998a7, 1002b13, 1059b3-9, 1069a34-6, 1076a17-21, 1077a11, 1080b11-14, 1080b23-25 and 1090b32-36. 3 Translation from Reeve 2016. The International Journal of the Platonic TraditionDownloaded from 12 Brill.com10/01/2021 (2018) 111-131 12:37:40PM via free access Mathematics, Mental Imagery, and Ontology 113 So, intermediates would be eternal, unchanging intelligible objects like the Forms, differing only in the aspect that they, unlike the Forms, are not unique. One of the main arguments for intermediates is that Plato’s metaphysics re- quires them due to the Uniqueness Problem.4 Recognition of the Uniqueness Problem can be traced back to Cook Wilson’s 1904 argument that the doctrine Aristotle referred to as “ὰσύμβλητοι ἀριθμοί” arose out of the fact that Forms are unique and thus cannot be the objects of mathematical operation and knowl- edge.5 For example, there is only one Form of Two, or, one twoness. In arithme- tic, we make statements such as 2+2=4. However, one cannot add twoness to twoness, because twoness is unique. This is why Aristotle describes the ideal numbers as “ὰσύμβλητοι,” translated as “incomparable” or “inaddible.”6 We en- counter the same problem with figures. Forms of geometrical figures, too, are unique, so, for instance, circularity cannot intersect circularity.7 Reasoning along these lines, many contemporary figures have argued as follows. Plato believed the theorems of the mathematical sciences are true. Due to his meta- physical commitments, these theorems, which must be true of something, can be true neither of Forms nor of sensible objects. Therefore, Plato’s metaphysics demands the existence of intermediates.8 The Uniqueness Problem provides only limited support for the claim that Plato held a theory of intermediates. As J.A. Brentlinger points out, this argu- ment is indirect, for it “is evidence for what Plato should have thought, or could have consistently thought, rather than for what he actually did think.”9 And, Plato does not himself use this reasoning in the dialogues.10 Other popular arguments given in support of Plato’s intermediates are based upon the cave 4 Annas (1975, p. 151) terms the problem formulated by C. Wilson “the Uniqueness Problem” in “On the Intermediates”. 5 Note that though Wilson’s reasoning is used to support the intermediates interpretation, he himself did not believe that Plato intended the objects of dianoia in the Divided Line to be intermediates. See C. Wilson (1904) 257-258. 6 C. Wilson (1904) 249-250. 7 C. Wilson (1904) 250. 8 Versions of this argument are found in H.S. Arsen (2012); J.A. Brentlinger (1963) 159-161; M. Burnyeat (1987) 221-222; M.J. Cresswell (2012) 95-96; W.F.R. Hardie (1936) 50; A. Wedberg (1955) 51-56; and C. Wilson (1904) 249-251. 9 J.A. Brentlinger (1963) 159. 10 J. Annas (1975) argues this in pp. 151-156 and 162-165. The International Journal of the Platonic TraditionDownloaded 12 from (2018) Brill.com10/01/2021 111-131 12:37:40PM via free access 114 Byrd allegory,11 Socrates’ treatment of faculties in Book 5,12 and Plato’s broader usage of αὐτό within the Republic.13 The tradition of interpreting the objects of dianoia as intermediates has been challenged by such figures as Reginald Hackforth, Francis Cornford, Richard Robinson, and Sir David Ross, who posit that they are Forms.14 Proponents of this view argue that the Divided Line is based on a contrast between the vis- ible and intelligible realms, and when this contrast is first introduced in lines 507b9-10, the intelligibles are explicitly identified as Forms. So, they conclude, it is reasonable to expect that both parts of the intelligible section of the Line have Forms as their objects.15 In addition, advocates of this position draw on 510d7-e1 in support for their interpretation. Describing the actions of the con- temporary geometers, Plato writes: “They make their claims for the sake of the square itself (τοῦ τετραγώνου αὐτοῦ ἕνεκα) and the diagonal itself (διαμέτρου αὐτῆς), not the diagonal they draw.”16 Since Plato typically uses the qualifica- tion αὐτό, or “itself,” to indicate reference to a Form, Socrates’ words are often taken as proof that Forms are the objects of dianoia.17 Though this group of interpreters agrees that the objects of both dianoia and noêsis are Forms, there is disagreement between individuals as to whether the Forms grasped by dianoia are different from those grasped by noêsis. On one view, the objects of the intelligible subsections are distinguished purely by the procedures by which they are studied: whereas the objects of noêsis are known in relation to the Good and the other Forms, the objects of dianoia are 11 For versions of this argument, see J. A. Brentlinger (1963) 156 and M. Miller 319. For an interpretation of this passage which argues against ontological intermediates as the ob- jects of dianoia, see J.T. Bedu-Addo (1979) 103-105; J.S. Morrison (1977) 228-229; P. Pritchard (1995) 101-103; and N.D. Smith (1996) 37-39. 12 This argument is found in J.A. Brentlinger (1963) 151, 158; M.J. Cresswell (2012) 96; and W.F.R. Hardie (1936) 51. See J.T. Bedu-Addo (1976) 290-291; R.C. Cross and A.D. Woozley (1964) 168; P. Pritchard (1995) 96; and R. Robinson (1953) 193 for a rebuttal. 13 M. Burnyeat (2000) 35-37 and N. Denyer (2007) 304-305 argue that Plato often uses “itself” to remove some qualification or “clutter” and could therefore be referring to intermedi- ates rather than Forms in 510d.