When the Roman emperor Cali-gula made his horse a consul, was he barmy - or ill? Similarly, when George W Bush collides with the English language, or turns global geopolitics into a cowboy film, is it just the homespun American way, this tendency to see the world in black and white, or is something more worrying at work?
It is commonplace to lament the growth of anti-Americanism. But you cannot escape how the US has become a begetter of cultural degeneracy. Its films are full of fights, explosions and car chases. Its porn industry is thriving. Much of its television is notable for prurience, emotionalism, lack of self-control - and more fighting. As for its food, think McDonald's and mourn. And how did the US convert a befuddled B-movie star into a charismatic president? Why does it have a penchant for intellectually challenged leaders?
Here, just possibly, is the answer. Last month, a survey found that junk food - sweets, snacks, soft drinks - makes up nearly one-third of all calories in the US diet, leading researchers to conclude that many Americans, despite being the fattest people on earth, are in fact "undernourished" in terms of vitamins and minerals. Other research, most recently from the environmental campaigning group WWF, has disclosed the increasingly toxic load of chemicals in our bodies - most of them ubiquitous in the developed world, especially those parts where capitalism has been given too free a rein.
Americans may thus be the planet's most comprehensive imbibers of food additives and synthetic toxins. Now consider the evidence of the impact of these on behaviour and intelligence. Flame-retardant chemicals can affect the memory and IQ. The connection between additives and hyperactivity, advanced by Benjamin Feingold three decades ago, was recently confirmed by the Food Standards Agency. The WWF study linked chemicals with reduced visual recognition and motor skills. American research has tied a tenth of neurobehavioural disorders to chemical exposure.
Could Americans be suffering a collective dose of ADHD (attention deficit hyperactivity disorder) - or worse, a kind of chemically inspired dumbing-down?
You may scoff at the idea. But consider the case of Caligula and millions of other Romans, poisoned - to madness, some think - by the proliferation of lead in their water, wine and liqueurs. Lead is a powerful neurotoxin - and so Romans suffered from reduced IQs, plummeting fertility, a propensity to violence and orgy, a liking for panem et circenses and a vulnerability to bizarre imperial behaviour. By the time Rome was sacked (by fundamentalist tribesmen) in 410 AD, it had already been eaten away from within.
Empires are often overthrown; but sometimes they poison themselves first.