Plato’s definition of justice in The Republic1 is based upon his division of the individual soul (psychē) and the state (polis) into three mutually interrelated parts. In this essay I will examine the structure of Plato’s analogy between the soul and the state in order to determine whether it is able to support a meaningful definition of justice in spite of charges of circularity and incoherence that are levelled against it. I will begin by considering Plato’s argument for the division of the soul into three logical elements, or parts, along with various objections to it, before moving on to consider the relationship between soul and state. In particular, I will argue that the precise nature of this relationship highlights a crucial aspect of Plato’s conception of justice that allows him to overcome the above criticisms of his analogy, which is more complex and subtle than might first appear.
In order to understand Plato’s analogy between soul and state, we must first be clear about what he means by the ‘soul’ and its ‘parts’. ‘Soul’ is the common translation of the Greek word psychē, which may also be rendered as ‘character’, ‘personality’ (Pappas 1995: 84), or even ‘mind’ or ‘self’. However, despite the religious connotations, its use in this context does carry any particular spiritual or theological significance. The terms that Plato uses to refer to the parts of the soul are similarly generic and suggest a general categorisation of impulses, or logical element, rather than the primarily constitutive role that the English word ‘part’ might suggest (Lee in Plato 2003: 140). It will be helpful to bear these points in mind in order to clarify various aspects of Plato’s account that might otherwise be obscured by an overly literal interpretation of the translated text.
II. The Three Parts of the Soul
Plato divides the soul into three distinct parts (illustrated in Figure 1) according to what might be called the ‘Principle of Opposites’ (Stalley 1975: 110). The principle states that, with respect to any aspect or part of an object, a single entity cannot apply opposing influences or be in opposing states at the same time (436b). The presence of such opposing influences may be taken to show that either (a) the influences must arise from two distinct sources, or parts of the source, or (b) that the influences affect two different aspects of the object being influenced (Stalley, op. cit.). Socrates’ examples of the man standing still while shaking his head (436c) and the spinning top (436d-e) are presented as examples of (a) and (b), respectively (Stalley, op. cit. 116). This is followed by a long discussion (437b–439d) intended to show that desires are simple, unqualified appetites for external things, and that their suppression by reason thereby falls into category (a), thus indicating the presence of two distinct ‘parts’ of the soul acting in opposition to one another, rather than two influences acting upon different aspects of the subject.
Figure 1: the three elements of the soul, with arrows indicating the rule of one part over another in the just individual through the virtue of self-discipline, or ‘temperance’
Many objections have been raised to this line of reasoning. Some (e.g. Kenny 1974: 18) relate to the apparent ambiguity of the phrase ‘with regard to same’ in 436b, and may be resolved by taking this to mean ‘in the same respect’, thus clarifying the difference between Socrates’ two examples (Stalley, op. cit. 113). Others question Plato’s treatment of pro- and anti-attitudes as opposites on the grounds that not being for something and being against something are not logically equivalent (Crombie 1962). Although Plato explicitly states in 437b that he does consider such attitudes to be opposites, he would in any case have found the idea of conflicting impulses originating from the same part of the psychē to be highly implausible on the basis of their still being opposed to one...