Thought I'd share my understanding of it.
In the allegory of the cave, Plato paints an image of prisoners who are shackled up within a cave and are in a state of immobility (Plato 514a). A huge fire rests high above and behind the prisoners is a source of light within the cave; the light aids in reflecting images and shadows onto a wall located in front of the prisoners (Plato 514a-b). The allegory is a reflection of Plato’s metaphysics and a thought experiment that exemplifies Plato’s understanding of how one obtains knowledge. After discussing his allegory of the cave, Socrates asserts the idea that an individual can only achieve knowledge by “turning-around” their whole soul (Plato 518b-d). Plato is arguing that education should not be a simple process of absorbing information. Plato believes that knowledge can only be attained through a reassessment of our reality and a complete re-examination of what individuals may hold as truths; attaining knowledge is therefore an individual cognitive process that requires self-evaluation in order to obtain higher understanding.
The allegory of the cave is Plato’s illustration of an individual’s ascent from the visible realm to the intelligible realm. The prisoners while shackled in the cave are subject to the lowest level of understanding and have no real knowledge. Their knowledge of the world is reduced to the shadows depicted on the wall; the shadows themselves are mere reflections of actual objects. When one of the prisoners is freed he is introduced to the material objects that produced the shadows that the prisoners held as true; the prisoner is overwhelmed and is unable to initially accept that his reality was an illusion (Plato 515c-e). The prisoner has to be dragged out of his false reality in order to begin a gradual transition into accepting the material world as it is; this transition involves moving his sight away from viewing reflections and shadows of objects to observing the objects themselves (Plato 515e-516b). Eventually the prisoner is able to view the sun and arrives at the conclusion that it is the sun that is the source of almost all that exists in the material world (Plato 516b-c).The freed prisoner after gaining understanding of the perceptual world would be unable to participate in the illusive reality of the prisoners in the cave due to his upward process towards the intelligible realm; the prisoners in the cave would even ridicule and outcast the freed prisoner because his upward ascent from the cave is viewed by the prisoners as detrimental to upholding the reality the prisoners have created within the cave (Plato 516c-517a). The prisoner freed from the cave had to turn his sight away from the darkness (which existed within the cave) towards the light (which existed outside the cave through the sun) in order to observe the material world as it is and not as it was depicted through the shadows within the cave. The allegory of the cave describes how knowledge is obtained. The cave is a representation for the visible realm. According to Plato, the visible realm is a reflection of the intelligible realm which is the realm of the Forms. Plato believes that for everything that exists in the world there is a unitary, perfect Form of that thing in another realm; for instance, the concept of beauty is often viewed in modern society as subjective, however, Plato would argue that beauty exists as a singular and perfect Form on its own. Our various views of beauty are attempts to reconcile with our understanding of the one true Form of beauty.
The light outside the cave and the sun represent the intelligible realm. This is better understood through Plato’s analogy of the sun. According to Plato, the individual sense of sight could only be possible through the light provided by the sun. Although there are other forms of light the sun provides the best light possible for the eye (Plato 508a). The light from the sun then makes sight possible in the material world. In the way that light from the sun provides vision to the eyes, truth and knowledge provide illumination and understanding for the soul. According to Plato, the Form of the Good is the cause of knowledge and truth and therefore superior to knowledge and truth; therefore it is not simply knowledge and truth that provide vision to the soul but the Form of the Good which gives truth and knowledge (Plato 508e-509a). Plato views the Form of the Good as the reason that all else can exist; everything in the cosmos owes its existence to the Form of the Good (Plato 509c). The sun outside the cave then becomes a metaphorical personification of the intelligible realm; this is the realm where the Form of the Good can be understood.
The prisoner that was set free from the shackles of the visible realm (the cave) ascended towards an intellectual journey that ended with a desire at understanding the Form that allows all else to exist, the Good (personified by the sun). The journey itself does not occur overnight, but rather it is a gradual process. Plato’s image of the line illustrates that there is indeed degrees that must be surpassed in order to finally arrive at understanding the Forms. Plato divides a straight line into four subsections of which two subsections fall into the realm of the visible and the remaining subsections fall into the realm of the intelligible; the realm of the visible is represented more greatly on this straight line (509d-e). The first subsection, which falls under the visible realm, represents images, reflections, shadows, and imitations of actual physical objects which constitute the second subsection of the visible realm (Plato 510a-b); Plato assigns the characteristics of imagination and belief to the first and second subsections, respectively (Plato 511d). In the allegory of the cave the freed prisoner moves from viewing reflection and shadows of material objects to the actual objects themselves and thus moves from an imaginative reality to a believable reality. The intelligible realm also has two subsections: the first reflects knowledge that is gained through hypothesis and rational deduction, such as mathematics, and the second and final section of the line is the knowledge of the Forms (Plato 510b-511d); Plato assigns thought and understanding with the first and second subsections of the intelligible realm, respectively. Therefore the highest understanding the freed prisoner obtained was that the sun is the source of all that exists in the visible world through rational hypothesis. This is symbolic for the intelligible realm in which the highest understanding comes from knowing the Form of the Good through rational deduction.
Plato therefore views the attainment of knowledge as the “turning-around” of the whole-soul because it is a cognitive process that requires a re-evaluation of what we perceive to be true reality. Initially, the freed prisoner did not want to accept that his reality was an illusion and instead wanted to remain shackled within the confines of his created reality in the cave; it was through observation and examination of life outside the cave that the prisoner realized the source of material existence and in a sense proceeded towards a journey of higher understanding. If an individual wants to understand the Forms then they must re-evaluate through thoughtful and rational deduction everything they perceive as the truth. For example, let us assume there is a hypothetical individual that wants to discover what true beauty is; this individual, through mass media indoctrination over the years, has arrived at the assumption that beauty is the white, European-descent, male or female that is fit. From the mass media, the individual only obtains a reflection of the Form of Beauty and his understanding of beauty is imaginative with no real knowledge. As the individual researches the topic of beauty further, he or she learns from social science scholars that beauty is a social construct. He or she now begins to view ideas of beauty as created by society and abandons his previous indoctrinated belief regarding beauty. Through rational deduction, he or she comes closer to understanding the Form of Beauty itself. His or her next step may involve finding evidence of beauty in everything in life. At this point he or she may use mathematical equations, such as the Golden Ratio, to determine similarities amongst beautiful objects. The more this individual learns about beauty the closer he or she comes to conceptualizing the Form of Beauty; the individual also gains knowledge to turn himself away from the original view that he or she had previously held. Plato feels that the whole soul must be turned-around in order to attain knowledge because an individual must question their own reality in order to transcend to a higher and truer reality.
The attainment of knowledge therefore becomes a self-evaluative task. Though the pursuit of higher learning can be engaged with others the actual re-evaluation of one’s perceptions of truth is primarily an individual duty. Plato views learning as a recollecting action in which the soul reconciles what it already knows; thus the attainment of knowledge as a self-motivated task seems more plausible since an individual must use rational understanding to reconcile occult or hidden knowledge found within the soul. An individual can only attain knowledge and “turn-around” his or her soul by examining one self. This is evident with the freed prisoner who refused to return to the cave after becoming more enlightened by his new reality. The prisoner knew at an individual level that his higher understanding of reality was more beneficial than to be deprived of knowledge by remaining shackled in the illusion of the cave.
Verification of what we perceive as true and review of our perceptual reality are key components to attaining knowledge. Insightful questioning of our reality and our perceptions of truth leads to attainment of knowledge that is often the product of personal growth through self-reflection. Thus, the attainment of knowledge becomes a self-evaluative task that requires a thorough understanding of oneself. Plato, through his image of the line, illustrates the successive steps of self-evaluation that an individual can follow in order to transcend to the intelligible realm. The end of all is to obtain the knowledge of the Forms and specifically the Form of the Good which allows all else to exist.