The Divided Line theory is a symbolic explanation of reality and the distinction between its two powers, namely the intellectual and visible worlds. Using this theory, Plato emphasizes the difference between knowledge and opinion. To explain the Divided Line theory, one should draw an imagined line and divide it into two unequal parts.
The first part represents the intelligible world, and the second resembles the visible world. Each of these two parts should also be divided into two unequal parts. The visible world part should now be separated into shadows and reflections on the one side and physical objects on the other side. These two subsections represent clearness and the wish to obtain clearness. However, the visual world is not completely true because it is constructed of opinion, which is changeable.
The second part of the line is the intelligible or intellectual world, represented by forms and intelligence. Using mathematical forms, one can learn about phenomena, not in the physical world. Furthermore, since individuals can understand mathematical forms, they exhibit intelligence, which is the second subsection of the intelligible part of the line. Thus, the Divided Line theory demonstrates that reality comprises complex elements of knowledge. However, there is no one truth or ultimate knowledge to be achieved due to the continuous change of factors and opinions, which ultimately change the knowledge.
The Divided Line theory is a persuasive philosophical account of reality and the essence of knowledge; however, it might not be fully consistent with modern science. In particular, various psychological theories differentiate between different levels of perception and cognition explained by brain functions that provide more clarity on how knowledge emerges. Therefore, the Divided Line theory should be primarily viewed as a philosophical framework rather than a scientific one.