Scottish polymath Thomas Carlyle famously articulated the concept in a series of lectures on heroism (later published as a book in 1841 titled On Heroes, Hero-Worship, and The Heroic in History).
Carlyle said that “the history of the world is but the biography of great men”. History is replete with great "heroes." These people have the power to shape and influence to such an extent that their absence would have meant an entirely different course of events.
While hugely popular in the 19th century, the theory fell out of fashion. In recent years, it has informed more time travel plots than historical analyses. Nowadays, it is more playfully deployed in fiction far more than fact. "What if we could kill Hitler as a baby?" is its signature question.
The war in Ukraine may just be bringing Great Man Theory back as a legitimate approach to history. President Volodymyr Zelensky has achieved the near-impossible of mobilising the Western world into believing victory is possible against Russian forces.
Zelensky channelled his inner Winston Churchill even though the British war leader's reputation is regularly rubbished. He is holding the line, inspiring his people and the world. Zelensky is irreplaceable at this exact moment.
His calls for the supply of planes and tanks from Nato is yet another parallel to Churchill's calls for aid from the United States in 1940. He is holding the line with great success.
Great Man Theory is back in full force, but this time we might call it Zelenskyism.
The danger of this theory is its greatest strength and, to make it a helpful analysis, it must avoid the pitfalls that led to it going out of fashion. When you become something more than just a man, you become a legend, and myths either receive god-like praise or can do no right.
Zelensky receives almost epidemic levels of fawning adulation with no hint of criticism against his conduct of the war. He is handsome, brave and charismatic. Western politicians and pop culture have been remarkably quick to imbue him with all the romanticism of great leaders past.
Great Man Theory is a phenomenal tool for understanding how a person's abilities, flaws, vices and virtues shape the world around them. This is often easier to understand in the negative – how would the West be reacting, right now, if the Ukrainian president was not possessed with the kind of characteristics which make him so likeable?
A revival of Great Man Theory requires a revised analytical toolkit. How much of the former comedian is genuine, and how much is an articulate, crafted and brilliantly executed exercise in propaganda? Zelensky has been spared the usual derision of politicians.
The war in Ukraine is arguably the first to be conducted on all social media fronts. Tweets, Facebook live posts and Instagram updates on presidential and military accounts are a slick media operation.
For all the attention placed on the people in Ukraine, theirs has not been the defining story of the resistance against Russia. The president is the lightning rod for the world's attention and veneration.
Cynicism must and should form a key component of Great Man Theory, and indeed, a healthy injection of it is what we need now. Zelensky is undoubtedly a competent leader, but the absence of any critical assessment is how personality cults are born.
We must differentiate between the propaganda because we want Ukraine to be victorious and pure hagiography. As the experience with Churchill has shown, that mentality leads to a chronically unhealthy approach in which “great men” are hijacked as heroes or bogeymen with few facts in between.
Most contemporary support for the Great Man Theory rests in its assertion that great leaders have abundant Big Five personality traits. Extraversion, agreeableness, conscientiousness, openness and neuroticism (with tendencies toward anxiety and depression).
One of the reasons this idea fell from favour was because it sought to inject faults with romanticism. Investment adviser and financial pundit Peter Schiff questioned Zelensky's choice of a t-shirt when addressing the US Congress. French President Emmanuel Macron was widely mocked for trying to cash in on the wartime look when posing unshaven in a special forces hoodie.
But the theory has relevance because Europe is being shaped by personalities once again. Vladimir Putin has single-handedly plunged his country into economic desperation and taken the rest of the world to the brink of war. Much more understanding can be achieved by analysing this man and his nature alone than labouring over the forces of history that have brought about these circumstances.
Accepting that history is made up of heroes and villains is something we have culturally lost. These days, there is a redemptive arc for every villain, and revisionism is often an effort to cast darkness rather than light on established figures.
The reality is thousands, often millions, played their part in history. At the epicentre, we find our great leaders, our villains, and their decisions.
Understanding these people and how they tick is critical to ascertain what they will do next. In an age where the map of Europe can be redrawn in the space of a month, this seems more critical than ever.
In the Scottish National Portrait Gallery, a section is dedicated to Heroes and Heroines. Churchill, who himself has a portrait there, once said: “Study history, study history.”
History is made up of people, and some deeds, and some people echo in eternity for a good reason. Zelenskyism is here to stay.