The Doctor, Romana and Duggan have found a painting hidden behind a panel in the basement of Count Scarlioni's house in Paris.
"It's the Mona Lisa!" says the Doctor.
"Must be a fake," replies Duggan.
The Doctor says he doesn't know what's currently hanging in the Louvre, "but this is the genuine article".
Duggan's astonishment increases when the Doctor folds back yet more panelling to reveal yet another Mona Lisa. And another. And another. Eventually, six identical copies are revealed.
"They must be fakes," says Duggan again.
"The brushwork's Leonardo's," the Doctor asserts, "It's as characteristic as a signature. The pigment, too."
"What," blithers Duggan, "on all of them?"
"What I don't understand is why a man who's got
six Mona Lisas wants to go to all the trouble of stealing a seventh." (The Count has been casing the Louvre, preparing to steal their Mona Lisa.)
This is Duggan's area. "Come on, Doctor, I've just told you. There are seven
people who would buy the Mona Lisa in secret, but nobody's going to buy
the Mona Lisa when it's hanging in the Louvre!"
"Of course," says Romana, "They'd each have to think they were buying the stolen one."
Because only 'the original' is valuable. These collectors wouldn't even want the Mona Lisa to sell or to display... they'd want it for - to use Duggan's phrase - the "expensive gloat".
But where does the value of the work of art lie? In its 'authenticity'? Huge amounts of time, effort, money and research are expended to establish the 'authenticity' of artworks; their provenance and history, tracing back to their origins. Experts compete over the 'authenticity' of various iterations of a single painting, fighting over which institution owns the 'real' one. Duggan, the private detective hired to investigate art as a catalyst of crime, responds to the Mona Lisas found by the Doctor with an instantaneous attempt to evaluate their 'authenticity', and hence their 'value'. (A set of assumptions that the Doctor explicitly rejects later in the show, when he mocks the idea that a painting needs to be x-rayed before its value can be ascertained.)
In the modern age, the 'age of mechanical reproduction' as Walter Benjamin put it, the artwork is viewed in a new and historically unique way. The camera destroyed the idea of timeless images arranged for a single spectator. The photographic representation cast painting adrift, since it usurped the painter's role as portrayer of the patron's property and ideology. Mass-reproduction of images destroyed the "aura" of a work of art (Benjamin's word for its unique and materially-intact history), making it seperable from its original time and place and locational context. The Mona Lisa, for instance, proliferated around the world. It is now no longer to be found in the Louvre. It is all over millions of greetings cards, the pages of magazines, the pages of books, posters, tourists' photos, the internet, the covers of execrable paperback novels. All this raises the fame of the painting while destroying its singular and unitary itselfness.
This very proliferation of copies is what makes the 'authenticity' of 'originals' so valuable as a commodity. The original is now just that: an original. It is something it never was before: the source of the millions of copies. As John Berger puts it: "the uniqueness of the original now lies in it being the original of a reproduction."
Scarlioni is really Scaroth: a ruthless and callous and self-involved warlord who found himself splintered into fragments across human history, manifesting in many different ruling classes over the centuries, as we see during his moments of trans-temporal communion. He is himself a system of copies, mass-reproduced, distributed across time and space, his uniqueness destroyed, each copy identical, none truly the 'original' because the 'original' Scaroth was destroyed... and all by technology.
He is a thoroughly modern man in some of his iterations, a man of power and property. He's a rich, titled, bourgeois art-thief in 1970s Paris, selling foundational objects of Western civilisation such as Gutenberg Bibles to fund his capers. He is one of the Borgias, or at least part of their coterie, acting as patron (i.e. employer and paymaster) to Leonardo, getting him to paint multiple copies of his portrait of Lisa Gheradini; copies which can then be hidden, so that his future self can unearth them. "A very nice piece of capital investment" as the Doctor puts it... a view that Scaroth can only take because he is part of modernity, from the Early Modern period which saw the rise of banking and commerce, to Late Capitalism which sees the commercialisation of absolutely everything. The irony which unites these eras along a single trajectory is the joke that, in this case, it was Leonardo himself who was payed/forced to begin the process of endless copying, reproduction and proliferation. All the copies are 'real', sharing an aura, made valuable by the same labour power of the same man... yet this wouldn't cut any ice with the collectors of the 1970s.
Scaroth's plan to reunite himself depends upon raising enough money to fund time experiments... and he plans to do this by selling the Mona Lisa seven times over, each to a buyer who thinks he's getting 'the original' (which, in a way, they would be!). But his scheme depends upon his ability to push humanity towards modernity - i.e. capitalism - because it is modernity that brings not only the necessary level of scientific and technical skill to make time travel possible, but also the rise of mass-reproduction, and thus the destruction of aura and the commodification of authenticity. Scaroth thinks of himself as pushing mankind on the path of progress... but his planned terminus of this progress is his reintegration at the cost of our annihilation.
Scaroth is a concentrated bundle of the nightmares of history. Borgia and bourgeois. Ruler, inscribing himself in the friezes telling the stories of the pharaohs. Warlord. "Insanely wealthy man." User and abuser of science via his ability to fund it. User and abuser of a wife who never really knew who he was underneath. Bringer of technological doom. Owner and destroyer of aura. A suave, handsome shell; a staring eye and a mass of writhing worms beneath.
He recalls another of Walter Benjamin's works: 'On the Concept of History', which is all about how the 'cultural heritage' is formed from the spoils of rulers who march onwards towards a future strewn with broken wreckage.