Are we heading for a Summer of Rage? A generation ago, young Americans flocked to San Francisco with flowers in their hair for a hippie Summer of Love. But today the potent combination of young people and sunny weather is producing something very different. The Sixties slogan was "Make Love Not War". The 2006 slogan seems to be the very opposite.
From Mumbai to Mogadishu, from Helmand to Haifa, the past week has seen an eruption of violence. Around 200 people were killed on Tuesday when a succession of bombs exploded along what was once Bombay's Western railway line. Suspicion fell on the Students' Islamic Movement of India and Lashkar-e-Taiba, the Pakistani-sponsored terrorist group, which seeks to end Indian rule in Kashmir.
In Somalia, meanwhile, Islamist extremists tightened their grip on the area around the country's capital. Reports of floggings for trivial violations of Sharia law suggest that the Horn of Africa has found its own version of the Taliban. For its part, the original Taliban continues to menace the British soldiers deployed in the Helmand province of Afghanistan, six of whom have been killed in the past weeks.
The crucible of this Summer of Rage, however, is without question the Middle East.
On Wednesday members of Lebanon's Islamist organisation, Hezbollah, attacked an Israeli border patrol, killing three soldiers and capturing two. Israel, already grappling with a hostage crisis in Gaza, retaliated by bombing targets in Beirut, including the city's airport, and blockading Lebanese ports. Hezbollah responded in kind by firing yet more of its home-made rockets into Israel. Meanwhile, the Israelis intensified their military pressure on the recently elected Hamas government in Gaza, where more than 60 Palestinians have been killed since the end of June.
All of which makes it tempting to conclude that the clashes in this Summer of Rage will mainly be between Muslims and non-Muslims. But wait a second. For the continuing violence in Iraq runs counter to that idea. This time last week, a gang of Shiite gunmen - possibly members of Muqtada al-Sadr's Mahdi Army - briefly took over Baghdad's mainly Sunni Jihad district and proceeded to murder around 40 people. This was just the latest in a succession of sectarian attacks by Shia against Sunnis or vice versa. According to the Brookings Institution, the number of such incidents recorded in May this year was 250, compared with just 20 in May 2005 and 10 in May 2004.
What this means is that, as I have been arguing for some time, the insurgency directed against American-led foreign forces is morphing into a civil war. Worse, as the former US Assistant Secretary of State, Leslie Gelb, recently warned, the cancer of sectarian violence has the potential to "metastasise into a. regional conflict".
Events in Lebanon show just how easily this can happen. For Israel is now no longer just fighting a Palestinian intifada in the occupied territories. It has all but declared war on a neighbouring sovereign state. And Lebanon is only one of several potential targets in the region. Both Hezbollah and Hamas are supported by Iran; the exiled leader of Hamas is based in Syria. Last week, Iran's ferociously anti-Zionist president, Mahmoud Ahmadinejad, phoned his counterpart in Damascus to promise a "fierce response" in the event of an Israeli attack on Syria.
No one should assume that this double crisis will simply blow over. Back in January, I raised the possibility of a "Great War of 2007", arising from just this kind of Middle Eastern "perfect storm". The best comment I got from a reader came in the form of a question: "So what makes you sure it won't happen this year?"
The Middle East is to our generation what the Eastern Question was to the Victorians: a baffling tangle of issues that defies simplification. It is hard enough just to figure out the rights and wrongs of the conflict between Israelis and Palestinians. By the time you have factored in the various Arab states, your head is aching. And you simply give up and reach for the Scotch when somebody mentions sectarian divisions in Iraq, or the factional politics of Iran.
Two things, however, are both simple and important. They are youth and heat.
Young people and hot weather are the common factors in all the conflicts that erupted last week, just as they played a part in the Summer of Love 39 years ago. The key differences are, first, that the proportion of young people is exceptionally high in the Middle East today, higher even than in the heyday of the Baby Boomers; second, that the temperature is a great deal higher in somewhere like Hebron than it ever was in Haight-Ashbury; and third, that Middle Eastern youths are much more likely to be poor and unemployed than their counterparts in the Swinging - and affluent - Sixties.
It is no coincidence that the most dangerous places in the world are among those with the most youthful populations. According to a recent study by Population Action International, countries where young adults (aged 15 to 29 years) accounted for 40 per cent or more of the adult population in 1995 had a one-in-three chance of experiencing civil conflict in the 1990s. Countries where young adults were 30 per cent or less of the adult population were far less likely to (a probability of just 11 per cent).
In Britain today, young adults account for just 23 per cent of the adult population. In the United States, the figure is 26 per cent. In Iran, however, the proportion is twice as high as it is here - 49 per cent. It is the same in the Occupied Palestinian Territories. In Iraq, it is 48 per cent. In Jordan, it is 46 per cent. In Syria and Somalia, it is over 50 per cent.
Young men are innately violent, as the parents of teenage boys will readily confirm. (I write with feeling on this subject, having been shot in the face by my 12-year-old son's BB gun last week.) But they are much more likely to give vent to their violent urges if they are hot, poor and unemployed. This is precisely the predicament of the youths of the Middle East.
Take Syria. The average July temperature in Damascus is 80 degrees Fahrenheit, unmitigated by widespread air-conditioning, compared with a mild 60 degrees in San Francisco. Per capita gross domestic product in Syria is less than a tenth of what it is in the United States. And the youth unemployment rate is a whopping 26 per cent.
Forget, for a moment, the terrible technicalities of Middle Eastern politics. Those straightforward figures give you the essentials. They explain the difference between hippies and Hezbollah. They explain the difference between swingers and suicide bombers.
And yet these problems are by no means unique to the Middle East. Sub-Saharan Africa and parts of Asia (notably Indonesia) are also bedevilled by the toxic cocktail of idle youth and sweltering heat. The mayhem that has prevailed over the past decade in places like northern Uganda and central Africa provides a reminder that Islam is by no means a sine qua non for strife.
And the West? Europe's "youth bulge" came in the first half of the 20th century. Twice - in August 1914 and September 1939 - the bored young men of Europe were mobilised in high summer for what proved to be the biggest wars in human history. Nothing like that could happen today, we tell ourselves, and in large measure that is true. We are, on average, much too old and timorous for another world war; we would rather cultivate our gardens, thank heavens.
Or would we? The fact is that there are still pockets of angry young men to be found in Europe, in communities that are increasingly susceptible to the reverberations of Middle Eastern politics.
Perhaps all the banlieues of Paris or the backstreets of Bradford need is a few scorching weekends for the Summer of Rage to happen here too.