The Rational/Non-Rational Distinction in Plato's Republic Todd Stuart Ganson
Plato's division of the soul in Republic X differs from the division in Book IV in a couple of obvious ways. First, the argument in Book X is an argument for two parts of the soul, while the argument in Book IV defends a tripartition of the soul. Second, while the argument for tripartition at 436-41 focuses on strife among desires, the argument for bipartition at 602-3 introduces examples of conflict among beliefs. In spite of these differences, the two discussions seem to share the common goal of drawing a contrast between rational and non-rational psychological states.1 My concern here is with this common goal of the two discussions. I will be defending an interpretation of Plato's distinction between the rational and non-rational.
The arguments for dividing the soul in Book IV have received far more attention than the ones in Book X,2 but there is a certain danger involved in attempting to understand either text in isolation from the other.3 In both passages Plato hopes to establish the presence of non-rational psychological states in humans, and there is every reason to suppose that he takes the desires and beliefs in question to be non-rational in the same sense. Accordingly, our understanding of the conclusions reached in Book IV should be responsive to what is said in Book X, and vice versa. Ideally, we want an interpretation of the rational/non-rational distinction that fits both texts.
What accounts, then, for the relative neglect of the division in Book X on the part of those interested in Plato's distinction between the rational and non-rational? There is, of course, the fact that the argument in Book IV lies at the heart of Plato's moral psychology and his response to Glaucon's challenge, whereas the argument in Book X figures in an attack on poetry that seems somewhat peripheral to the central project of the Republic. Further, some have thought that in Book X Plato is arguing for some sort of division within the rational part, not a division between the rational and non-rational as in Book IV.4 Yet another factor, I suspect, is that philosophers find Plato's appeal to conflicting desires in Book IV much more promising philosophically than his appeal to conflicting beliefs in Book X. The latter argument is seen more as an embarrassment best left to the side. My overarching goal here is to counter this assessment of Plato's argument. Plato's attempt to distinguish rational from non-rational cognition should be recognized as one of the more impressive moments in the Republic.
But whatever the sources of past neglect may be, in the last few years the trend has changed. Consider first Hendrik Lorenz's recent book The Brute Within, which has an entire chapter devoted to the crucial argument in Book X at 602-3.5 Lorenz spends most of the chapter discrediting the view that Plato is here dividing reason into two parts. He offers a compelling defense of the idea that Plato is arguing for "a division between reason on the one hand and a non-rational part on the other."6 But after showing that Book X is in this respect consonant with Book IV, Lorenz leaves us wondering what, exactly, this division between the rational and non-rational amounts to. In his treatment of the discussion of appetitive desire in Book IV, Lorenz concludes that the rational part is distinctive because of its capacity for means-end reasoning—it is precisely this form of reasoning that is lacking in the non-rational, appetitive part.7 However, when the topic turns to Book X and non-rational beliefs, Lorenz does not tell us how to extend this account of non-rationality to the case of belief. He does say in passing that our non-rational side forms beliefs uncritically,8 but he never explains what makes non-rational beliefs non-rational.
Of course, it is always possible that Plato has changed the sense of "rational" as the topic moves from desire to belief. It is unlikely, however, that Lorenz wants to propose an interpretation along these lines. As he notes, "book 10…contains a number of back-references to the argument for tripartition of the soul in book 4, all of which suggest continuity and none of which as much as hints at revision."9 Plato is evidently employing the same vocabulary to draw the same kind of contrast in both texts, a contrast between rational and non-rational psychological states.10 With his appeal to conflict among beliefs in Book X, Plato is attempting to illustrate the same type of division he uncovered among desires through his examples of mental conflict in Book IV.11
Lorenz has advanced discussion of Plato's division of the soul considerably by demonstrating continuity between Plato's aims in Book IV and Book X. What is needed still is an account of what, exactly, Plato is arguing for in these texts. What is this distinction between the rational and non-rational that applies as much to beliefs as to desires?
In her recent paper "Appearances and Calculations: Plato's Division of the Soul" Jessica Moss confronts this question head on, developing a novel approach to Plato's distinction:
[…] we discover in Book 10 that what it is for a part of the soul to be non- rational, with all that that entails for its ethical status, is for it to accept unreflectively that things are just as they appear to be, while what it is for the rational part to be rational, with all that that entails for its ethical status, is for it to be able to transcend appearances by calculating how things really are. These are the defining features of rationality and non-rationality, which unify and explain the various traits of the parts of the soul and their various characterizations throughout the dialogue.12
Book X reveals that the non-rational side of the soul is limited to cognizing appearances—it is incapable of weighing evidence or calculating which option is best.13 What non-rational beliefs and desires have in common is that they are uncritical responses to appearances. The non-rational part just accepts as true however things appear to be and desires whatever appears good. One interesting consequence of this approach is that Moss is committed to rejecting the familiar view that Plato's appetitive desires are good-independent (i.e. having an appetite for something does not involve or depend upon cognizing it as good).14
In what follows I will be developing a very different approach to Plato's distinction between the rational and non-rational, one in line with the view that appetites are good-independent. After setting out my reading, I raise some difficulties for Moss' account. I conclude with a positive assessment of Plato's strategy for distinguishing rational and non-rational parts of the soul.
At Republic 602-3 Plato observes that someone subject to a visual illusion may at the same time make a correct judgment regarding what she sees. Plato takes these to be cases of