On the other side of a city canal was a public park. Seated in the park was a woman dressed in the full chador, the head-to-toe black, sheetlike covering favored by the most conservative elements in Iranian society.
There was nothing unusual about that sight. But this woman was with a male companion. She was resting her head on his chest and every so often would lift her face, presumably -- I wasn't close enough to tell for sure -- to either kiss him or whisper to him.
If a couple in the West behaved in that way, it would seem merely romantic, even quaint. But this was the Islamic Republic of Iran, where hundreds of women have been arrested for purportedly "un-Islamic" modes of dress since the government of President Mahmoud Ahmadinejad began its spring crackdown.
And it is where the Moral Police -- yes, that is the name by which they are generally known -- are prone to stop and question couples in the street if they suspect they are unmarried.
In that context, the chador-wearing woman's tender behavior was nothing less than an act of rebellion against the forces of the state -- and one requiring a sizable dollop of courage.
In liberal societies like our own, we tend to worry about whether sexual behavior has become too permissive and sexualized imagery too widespread. But to travel to somewhere like Iran is to be reminded that our impulses for love, affection and sex itself have the potential to break bonds of repression and shake a society up for the better.
In general, discussions of society and politics too often neglect the importance of sex.
Six years ago, I reported from Israel and the territories. When it came to describing life in Palestinian areas, I wrote about the posters of martyrs that seemed to grace almost every wall and the fiery speeches against America outside the local mosques.
But I didn't report that in almost every Internet cafe I went into, teenage boys clustered three or four to a computer, transfixed by pictures of Britney Spears. At the time, I thought Spears was too ephemeral to mention. Wrong again.
The tension was worth exploring between an increasingly Islamic political culture, where the United States was customarily referred to as the "Great Satan," and a social culture, where young men lusted after an American pop star and craved the sexual freedom she seemed to represent.
It may be entirely possible to hate America and fancy Spears, but the teenagers' lust at least suggested that they were unlikely ever to conform to every stricture their most hard-line leaders wished to impose upon them.
In a place like Iran, sexuality is arguably even more important. A leftist economist, Fariborz Raees Dana, who told me how he had suffered beatings and been fired from university positions for his political views, insisted that "the sexual want of the people'' was one of the main motivations for social change.
Certainly the "chadori" in the park seemed far from alone in challenging the restrictive limits of her society. The young Iranians who have raised flirtation to an art form and the young women who do their best to subvert the strict dress codes with high heels, scarves pushed far back on their heads or form-fitting manteaus are cutting away at the restrictions imposed upon them by fundamentalists.
Repressiveness on sexual matters is by no means confined to Islamic regimes. A report earlier this year by the French group, Reporters sans Frontieares, noted that the government of Sri Lanka summarily closed a radio station for having the temerity to broadcast a show about sexuality.
The past century is rich with Western examples of the kind of oppressive hysteria about sex that we now mock or condemn elsewhere. Witness everything from the injunction against showing Elvis Presley from the waist down in his early television appearances to the infamous decision by some Irish farmers to march against jazz in the 1920s.
George Orwell's fictionalized totalitarian regime in "1984" sought to expunge all sensuality from its subjects' lives:
''The aim of the Party was not merely to prevent men and women from forming loyalties which it might not be able to control,'' Orwell's hero Winston Smith lamented. ''Its real, undeclared purpose was to remove all pleasure from the sexual act. Not love so much as eroticism was the enemy, inside marriage as well as outside it."
He later wrote, ''A real love affair was an almost unthinkable event.... The sexual act, successfully performed, was rebellion. Desire was thought crime."
Orwell cuts to the heart of the matter as usual.
Repressive governments of whatever stripe distrust the sexual impulse because it is, at base, anarchic, idiosyncratic and in some sense ungovernable. The woman in the park in Tehran, and many other people across the world, are helping erode the cold bonds of authoritarianism and oppression.
The only weapon they use is their own humanity. It's powerful enough.
Niall Stanage, a journalist from Belfast, Northern Ireland, is a columnist for the Irish national newspaper, The Sunday Business Post. He is based in the United States.