So the sun is not to be identified with sight, but is responsible for sight and is itself within the visible realm… As goodness stands in the intelligible realm to intelligence and the things we know, so in the visible realm the sun stands to sight and the things we see. (VI, 508b–c)
Plato leaves the world of the senses with the doctrine that there is a permanent and unvarying reality, a divine and orderly world ‘where wronging and being wronged don’t exist, where all is orderly and rational’ (VI, 500c). This is obviously distinct from the shifting scenes of ‘plurality and variety’ (VI, 484b) which the senses show us, and in which normal life is lived. He holds the view that this reality is alone the subject of knowledge, and he is in no doubt that such knowledge is possible, although it is demanding, and only ever achieved by the elite few, the philosophers or lovers of knowledge who have undergone an arduous education before becoming capable of it. Finally, there is the view that this reality provides a foundation for ethics and right conduct. It somehow certifies, all by itself, what is virtue and what is not.
Within that framework, variation is possible. The key issue will be how to think of the relation between the ‘transcendental’ reality, and the world of the senses, which is after all the world in which the elite have to act, and which they are apparently qualified to rule. Plato is well aware of the problem: immediately after the passages we have been looking at, he confronts the objection that philosophers, or at least people who do not drop it after an initial dabbling education, ‘turn out to be pretty weird (not to say, rotten to the core)’ (VI, 487d). Socrates urges that philosophers are bound to be disrespected by the vulgar, precisely because they are vulgar, and therefore incapable of appreciating the true expertise that the philosopher brings to the civic community. But worse than that, in an imperfect state, the insidious corruptions of flattery and mass adulation will deflect any human being from the course of philosophy into the hurly-burly of unilluminated argument and politics. Finally, up-starts and pretenders will gatecrash philosophy, pretending themselves to possess the knowledge of the philosopher, and to the majority of people they are indistinguishable from the real thing.
All these are obstacles, serious if not entirely insuperable, to establishing the rule of the elite, the philosopher-kings. They boil down to a chicken-and-egg problem. The philosopher can only grow in the ideal community, but no community can be ideal unless already under the rule of the philosopher. To break the log-jam, it would take a ‘trembling hand’, a random generation of one of the necessary ingredients, after which, perhaps, both individual and community could lever themselves up the path to perfection. But by itself none of this gives us a model for the kind of Enlightenment which is needed for the philosopher-ruler.
What we need at this point is a more concrete illustration of what the elite knows, and how they bring that knowledge to bear on the everyday realities of decisions and choices. Instead, Plato gives us three images, those of the sun, the line, and the cave. The sun, in this metaphor, illuminates and lights up the visible world. Plato also suggests that it changes the things we see. At least, in the application of the metaphor:
Well, here’s how you can think about the mind as well. When its object is something which is lit up by truth and reality, then it has – and obviously has – intelligent awareness and knowledge. However, when its object is permeated with darkness (that is, when its object is something which is subject to generation and decay), then it has beliefs and is less effective, because its beliefs chop and change, and under these circumstances it comes across as devoid of intelligence. (VI, 508d)
Again we have the identification of reality, the proper object of knowledge, with the unchanging. The metaphor of the sun does not really help much with this: after all, in sunlight we see things that change just as we do in artificial light or poor natural light. Sunlight does not freeze things. All the metaphor really gives us is a vague idea of a permanent ‘illumination’. Continuing, however, Plato compares the light cast by the sun with the knowledge and truth illuminated, or brought into view, or even created, by goodness itself. For goodness confers ‘reality and being’ on the things we know (VI, 509b).
This is hardly convincing, so to supplement the simile of the sun Plato gives us the next image, which is that of the divided line. We are to imagine a line divided into two unequal sections, with each section divided in the same ratio to two further sub-sections. In the first section of the line there is knowledge of a ‘visible realm’ consisting of likenesses, shadows, reflections, and so on. Then in the second section are the things whose likenesses are found in the first section: ‘all the flora and fauna there are in the world, and every kind of artefact too’ (VI, 510a). These together form the realm of belief, and the two sections of shadows and everyday objects stand to each other as this realm stands to the realm of knowledge – in other words, belief is to knowledge as shadow is to original. But the realm of knowledge is itself divided. Next up then is the world of the ‘likenesses’ which geometers use: particular diagrams, for example. Although they use these things, the object of their study is to transcend them and obtain a purely abstract understanding of geometrical forms. A diagram (which may be blurry or ill-drawn or made up of thick lines and skew triangles, and so forth) is an aid to the abstract thought, but not itself the subject-matter. Pythagoras could have worked out his famous theorem staring at a pretty terrible drawing of a right-angle triangle. But what he then contemplated was the second and highest division of the realm of knowledge (and so the fourth segment of the line). Plato associates it with the transcending of sense experience, and the arrival at a point at which nothing need be taken for granted. It is ‘what reason grasps by itself, thanks to its ability to practise dialectic’ (VI, 511b).
It can’t be said that the metaphor of the line helps very much. There is much to dislike in the whole set-up. In the initial two sections of the line, there is the implication that the ordinary objects of sense experience are merely shadows or pictures or ‘likenesses’ even of everyday things, rather than those things themselves. But why should we accept that? When I see a book, I typically see neither the shadow of the book, nor a picture of the book. Plato is probably skipping down the permanent wrong turning in philosophy, which is to suppose that in order to cope with the phenomena of illusion and hallucination, we must analyse everyday straightforward perception into a ‘direct’ acquaintance only with a proxy for such things as books: a ‘sense-datum’, or some kind of see-through, mental picture of a book. The mind on this model becomes the spectator of a scene generated within itself, inside its own inner theatre, somewhere at the end of the optical and other processes whereby neurons and synapses deliver their ‘messages’ to it. This model of the mind and its perceptual objects is generally regarded as tempting but untenable – one sign of its untenability being that it is a royal road to scepticism, or the consequence that we are forever trapped within the selfsame inner theatre, with no access to objects outside. This is not the place to detail all the ways in which modern philosophy has sought to dismantle the idea. It is enough to signpost it as a dead end.1
Many philosophers have fallen for the picture of the mind as an inner theatre, and therefore acquainted with mere shadows, illusions or images – proxies standing in for external things. But usually they put up with two levels of reality: that of ideas or images (the shadows) and that of real external things themselves. Plato is much more complex, using the line to model a four-fold division of reality. The next layer is indeed that of ‘ordinary’ things, things that are changing, including such everyday things as flora, fauna and artefacts. However, these cannot themselves be objects of knowledge, but not because we fall victim to scepticism whenever we try to get one step beyond the images in the inner theatre. Knowledge is going to leapfrog this layer entirely, and land even further from private experience. Plato relegates these things to the realm of mere belief, apparently on the grounds that they change, but why? I can know that I have flowers in my room, what kind they are, and indeed how long they are likely to last, although all the time they are changing. The prejudice against the ordinary world seems to come from nowhere, or perhaps as Nietzsche thought, from some deep hatred of ordinary life.
When we finally do come to the realm of knowledge, we meet the distinction between geometry done by means of diagrams and geometry done with no recourse to diagrams but purely mathematically. The first, it is implied, is interesting enough, and gives us a kind of knowledge of an inferior variety. But the fourth is the real thing: circles and right-angled triangles, squares and polygons, in all their unchanging, glorious abstraction. However, there is still no hint of how to deploy the exalted status of mathematical objects in any practical way – in the world of ethics or politics, for example.
So the image of the line is more confusing than enlightening, and we turn to Book VII of Republic, and the most famous metaphor in the history of philosophy – the resonant allegory that everyone remembers, and that even people with minimal exposure to philosophy itself have probably heard of: the Myth of the Cave.
In this fantastic image the plight of ordinary, uneducated, unenlightened humanity is compared to that of prisoners in a cave. It is a rather peculiar cave, however. They are tied so as only to see the back wall of the cave. Matters are arranged so that behind their backs is a fire, and a kind of roadway along which are carried all sorts of statuettes and animal models, puppets or marionettes. The fire casts the shadow of these artificial things on to the wall the prisoners see: ‘the shadows of artefacts… constitute the only reality people in this situation would recognize’.
Ascent from the cave happens when one of the prisoners is released, and made to turn and see the marionettes themselves, and the fire. This unfamiliar sight would frighten and bewilder him, habituated as he is to the world of shadows (in terms of the line he has now reached the second of the four stages). Further ascent takes the ex-prisoner up ‘a rough steep slope’ to the world of daylight, which again is unfamiliar and overwhelming. Gradually, however, he would begin to make out the real things of everyday life (now apparently corresponding to the third section of the line rather than the second). And then, the last thing he would do is to make out the heavenly bodies and the sun itself, ‘not the displaced image of the sun in water or elsewhere, but the sun on its own, in its proper place’. This is the pinnacle of understanding, the last illumination, an acquaintance with the Form of the Good itself. Whatever that may be.
Perhaps the power of this tremendous allegory is directly proportional to its lack of specificity. Just as with the initial distinction between knowledge and its domain, versus belief and its domain, or with the image of the line, it is far from clear how to interpret the ascent Plato demands, or the procedures of education or illumination that would further it. European and Islamic thought has generally followed one of three broad models.