*This post is intended merely to recount Plato’s ‘Divided Line’ concisely, not to ask and (attempt to) answer all the relevant questions.
We all know that, for Plato, the highest form about which one may inquire is the good. He writes, in the Republic (VI, 504e), for example, that, “the form of the good is the most important thing to learn about…” Unfortunately, however, when his interlocutors implore him to “discuss the good as [he] discussed justice, moderation, and the rest,” Socrates declines, saying, “I’m afraid that I won’t be up to it and that I’ll disgrace myself and look ridiculous by trying” (VI, 506b-e). What he can do, however, is discuss the visible reality that is most like the good. This leads to a distinction between two orders of things: the visible and the intelligible.
The good, as indicated above, is the highest reality in the intelligible order (which, of course, makes it the highest reality of all). The highest visible object is the sun. How does the sun relate to our visible order? Consider that we have the power of sight. This is made possible by the presence of light; the sun, Plato said, realizes our power of sight. It is the first visible offspring of the good; the sun most manifests the nature of the good (notice a significant analogy: one cannot look directly at the sun, at least without paying a steep price). Things are as invisible in the absence of the sun’s light. Similarly, without the good one’s soul cannot grasp “truth and being,” each of which flow from the good and illuminate intelligible objects (e.g., the form of justice). Attempting to grasp forms without the illumination (i.e., the “truth and being”) of the good results in failure, a.k.a., opinion (daxa); the soul is as though blind (like feeling your way around in the dark). This doesn’t mean utter failure; one does still attain opinions (which are at least something). This leads to Plato’s “Divided Line.” By the way, Donald Palmer, in his terrific intro text Looking at Philosophy: the Unbearable Heaviness of Philosophy made Lighter 2nd ed, does a great job of explaining (in a very elementary way) this material (pp. 51-67).
Here is an attempt at illustrating Plato’s ‘Divided Line’:
Perhaps the best way to approach Plato’s Divided Line is to think of it as an explanation of both his epistemology (“state of the soul “in the chart above) and his ontology (“objects” in the chart above). Man comes to himself in a world of sensible objects and images of those sensible objects. Sensible objects may be basically understood (not surprisingly) as objects we access via our senses (e.g., a particular horse, or a particular person). Images are just that—images of sensible objects: photographs, reflections in a pool of water, etc. As I said, we come to ourselves in a world filled with these things; they are all around us, and in one sense our lives may be described as our series of interactions with these things. Plato calls the state of our soul when it is apprehending images “eikasia” (trans. imagination or conjecture). The state of the soul when apprehending sensible objects he calls “pistis” (trans. faith, trust, or belief). Together these comprise the visible realm.
Consider these two states: that of eikasia and that of pistis. Why does Plato say that one is in a state of imagination or conjecture when apprehending images? “Because,” he explains, “this person mistakes the image for reality.” When you are at a lake, say, and you see the reflection of the trees on the surface of the water, you are seeing a mere image of the trees (the sensible objects). Notice the dotted line in my illustration. The lower one is on the line, the less “truth and clarity” one’s soul has in its grasp of the corresponding object. So, the soul has very, very little truth and clarity in its grasp of images. Plato continues on to explain that when we grasp sensible objects themselves, we are in a state of trust or belief. This leads to an interesting feature of Plato’s epistemology which I will largely ignore here: as I mentioned above, opinion (not knowledge) is the best one can attain in the visible realm. This is because we experience sensible objects via our senses, which can deceive us.
“Nevertheless,” “you may say, I’m getting along quite well with “mere opinion” here in my world of sensible objects.” In fact, why even bother with another realm, the realm of the intelligible?” That’s a frequently asked question, and it does have some prima facie appeal. Consider, however: isn’t an important feature of our lives our desire to (1) have greater clarity in apprehending sensible objects, and (2) achieve greater precision in predicting and controlling our experience with them? We are, admittedly. pretty good at simply encountering a sensible object and dealing with it with no real thought or effort. Most of us, though, desire something like (1) and (2), at least I do. What do I mean by (1), which may be less obvious than (2)? To illustrate: imagine you’re a guest at someone’s new house. In the middle of the night you get up for a needed glass of water, but it’s dark and you can hardly see your way around. As you approach the door, it appears to be open, but it turns out to be only half-way open. This becomes painfully clear to you as you walk nose first into its edge; you immediately wish you’d had greater clarity in your apprehension of the sensible object. There are, of course, more and more serious examples to be had, but I think this one makes the point nicely.
When we begin the pursuit of (1) and (2), we typically do so by engaging in some techne or other (an art [not fine arts]; for more on this, see lines 510b and following in the Republic). This is how we break into the intelligible realm. We come to see sensible objects as themselves images (reflections) of mathematicals (the lower intelligible structures). The state of our soul is now dianoia (thinking); we come to see these as the originals for sensible objects. It’s something like how we see a blueprint as the original for a complex bridge before it’s construction. We consider many (very important) theories, such as how much weight certain materials are rated to hold, how much distance can be between supports, what direction ought the bridge face, environmental concerns, etc. Notice that the states of dianoia and pistis are directed at the same field of things: sensible objects. For Plato (and this is the distinctively Platonic move), one engages in dianoia while focusing on the sensible objects (as explained above); notice they have the same ratio (of 2). The difference is that, while focused on and thinking about sensible objects, when one engages in dianoia, one comes to see the sensible objects differently.
At this point things get a little sketchy. Finally one is in a position to see that even the mathematicals are not the highest reality. We’ve been to this point focused on the sensibles, but, Plato says, these are not where it’s at. The theories and definitions with which one grappled while in dianoia are merely images of the highest reality: the forms. In dianoia we are engaged in providing postulates for the foundation of our dealing more precisely with sensible objects. However, these hypotheses (postulates) are at this state taken for granted.
And now the big turn. One comes to inquire into the foundations of those postulates (an inquiry Plato calls dialectic). Are the postulates themselves grasped with truth and clarity? Upon realizing that, no, they really aren’t, Plato says we must redirect our soul upward (whereas we have so far been focused down the line, toward the sensible objects; cf. the picture at the top of our blog, “the School of Athens,” in which Plato [the guy on the left] is pointing upward) toward the forms, the source of sources with which we’ve sought to clarify our apprehension of sensible objects. These are free of hypotheses and suppositions. Here the starting points of thought are no longer taken for granted. It is then that one is finally in a state of noesis.
Plato’s Divided Line is complicated, especially when you’re reading someone’s attempt at summarizing it. Go, read Plato’s explanation! After that, read his own illustration of it in his Allegory of the Cave, which helps things make more sense. If you’re really interested, go on to his so-called Third Man argument against his theory of the forms. And remember—people spend their entire lives attempting to understand Plato, so if it’s not immediately clear, continue seeking greater truth and clarity in your apprehension!