A mathematical investigation by an Oxford professor has challenged one of the most enduring claims about the Parthenon: that its subtle curves and architectural refinements were deliberately designed to correct optical illusions.
For more than two millennia, scholars and architects have admired the Greek temple overlooking Athens and credited its builders with using sophisticated geometry to ensure that the structure appeared perfectly straight and balanced to the human eye.
But Prof Alain Goriely of the University of Oxford has reached a very different conclusion after examining the mathematical evidence behind the theory.
According to his study, published in Royal Society Open Science, many of the optical effects supposedly corrected by the Parthenon’s architects are either unsupported by evidence or too weak to be perceptible.
“I do think it might be the oldest myth that we have,” Goriely said, “apart from religion.”
The myth of the curved foundations
One of the best-known examples concerns the temple’s base, or stylobate. Measurements show that the long sides are not completely flat but rise gently towards the centre, by around 6 centimetres.
The traditional explanation is that the architects introduced this curvature to counter an optical illusion that would otherwise make the base appear to sag in the middle.
Goriely examined two possible explanations for such an effect and found little evidence for either.
One theory holds that long horizontal lines naturally appear to dip towards the centre. His analysis found no convincing evidence that such an illusion occurs in the way required to explain the Parthenon’s design.
The second explanation involves the temple’s columns and the so-called Hering illusion, in which parallel lines can appear curved when intersected by other lines. However, the effect is strongest when the intersecting lines meet at relatively sharp angles.
The Parthenon’s columns are almost vertical, making the effect too weak to account for the curvature of the temple’s base. There is also no clear evidence that the illusion operates in the same way in three-dimensional structures.
The columns may not be correcting vision either
Another celebrated feature is entasis, the slight outward curvature of the Parthenon’s columns.
The conventional explanation is that the columns were deliberately made thicker in the middle because perfectly straight columns would appear unnaturally narrow at that point.
Goriely again found little evidence supporting the theory.
The columns bulge by only around 18 millimetres, a difference that would be barely noticeable from normal viewing distances. The supposed optical illusion that the curvature was intended to correct is also difficult to demonstrate.
His study examines and dismisses several other proposed examples of optical correction, raising the possibility that the Parthenon’s architects had entirely different reasons for incorporating the curves.
A practical or aesthetic explanation?
Goriely suggests that some of the features may have had practical purposes. The slight curvature of the base, for example, could have helped prevent rainwater from collecting on the temple’s surface.
Other design choices may simply have reflected ancient Greek aesthetic preferences. Curved columns could have appeared more natural or visually pleasing to their creators without being intended to compensate for a specific defect in human vision.
The persistence of the optical-correction theory may partly reflect the extraordinary reputation of ancient Greek civilisation for mathematical and architectural sophistication.
A story dating back to antiquity
Goriely traces the origins of the theory to the Roman architect and engineer Vitruvius, who wrote about Greek architecture roughly four centuries after the Parthenon was built.
His explanations were subsequently repeated in architectural literature and gradually became accepted as established fact. The theory has proved remarkably resilient, even appearing in explanations generated by modern AI systems.
Frank Salmon, professor of the history of classical architecture at the University of Cambridge, said some scholars had long been cautious about treating Vitruvius as an authoritative guide to Greek architectural practice.
He noted that Vitruvius was writing centuries after the Parthenon was constructed and that many of the original Greek texts on temple architecture that he claimed to have consulted have since been lost.
Goriely acknowledged that investigating the evidence became something of an obsession, describing how he “fell into a bit of a rabbit hole” while assembling the research.
He ends his study with an unusual invitation for an academic paper: put the research aside, go for a walk and look for yourself.
“Trust your own eyes, question what you see and decide for yourself whether the theory of optical corrections holds up,” he writes.
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