Admittedly, drawing a correlation between the fluorescent light-fixture art of Dan Flavin and the teachings of one of Greek philosophy's founding fathers might be a stretch.
For one thing, the time difference separating the two men is massive: Flavin's major works spanned the 1960s – 1990s, and Plato published The Republic in 380 BC. One man was a minimalist artist, the other was a philosopher who believed that art is a mere imitation of physical form and is, therefore, ultimately an illusion.
What could possibly connect this unlikely pair, who at first appear to be so very, very different? The answer is simple: light.
Yes, light. If you haven't recently had a chance to brush up on your Greek Philosophy 101, Plato is actually very well known for his discussions about light. In The Republic, he presents the reader with "The Allegory of the Cave." It describes a group of prisoners who are kept in a cave for their entire lives, and whose entire basis of existence is composed of the various shadows and echoes of their environment. The world, as they know it, is cold darkness, simply because they don't know any better.
However, if these same prisoners are released, and are allowed outside the cave to behold the Real World, they must face the fact that their existence in the cave was limited, a shadowy illusion of reality. In fact, they can now witness their "true" reality, thanks to the light generated by the sun.
Plato considered light, particularly sunlight, to be the ultimate "bearer of truth." Due to the popularity of Plato's writings among several medieval religious groups, this correlation was responsible for Gothic stained glass windows, Byzantine mosaics, and other spiritual associations between light and divinity, and light as divine truth.
Dan Flavin entered into this tradition of light and truth roughly two thousand years later. His Icon series directly references light's divine implications, since an "icon" originally referred to a religious work of art in the Catholic and Eastern Orthodox religions. Similarly, his Diagonal of May 25, 1963 (to Constantin Brancusi) was described by Flavin as his own "diagonal of personal ecstasy."
Flavin won't be the last artist to utilize light to represent purity, truth, or spirituality. But through his work, Plato's tradition of light as truth has persevered through the centuries.