Some change happens very quickly. Occasionally the thing that has been accepted for generations disappears very quickly. I’m too young to remember the women’s struggle to vote, but as I look back at the history of the vote, it seems that once it really began, it happened right away.

I’m not too young to remember the birth of feminism. I grew up believing that I’d probably be a mom, but I might teach kindergarten. There weren’t really any sports for me to play, although I did get into a synchronized swimming program in high school. When I graduated from college, I no longer wanted to teach kindergarten and I wasn’t married so I went to typing school. But the change came, and it came in a big hurry. Five years later, I was supporting myself as a financial advisor, teaching investment courses and writing about ethical investing.

I’m not too young to remember the end of smoking. When I was pregnant with my son, who’s now 30, the small office I shared with four others was always full of smoke. In fact after lunch, it was full of cigar smoke. It never even occurred to me that I might ask my fellow workers to show some consideration to a pregnant and uncomfortable woman. But once the ball got rolling, smoking was banned in setting after setting.

Then comes the toboggan slide, when laws, social norms and manners all come together to assist, rushing to embrace the new understanding.

The process of long-term sustained change seems to involve a few vital components. First, one needs a countervailing thesis. Women are as much citizens as men are. Smoking is unpleasant and harmful to non-smokers. Next, you need some people to get really, really worked up about it. This vanguard has to be brave about confronting people who disagree with them. After that, the notion is aided by righteousness. Only a fool would consider his wife, mother, daughter or sister incapable of thought. Only a selfish jerk would poison his or her family and friends while poisoning one’s own body. Then comes the toboggan slide, when laws, social norms and manners all come together to assist, rushing to embrace the new understanding.

Recently I got a wedding invitation in the mail.  Tommy and Brian were getting married. Because Tommy and Brian live in Massachusetts, this same-sex couple was granted access to the institution of marriage, but in most of the U.S. they would not have had the option. Still, it feels a lot like the “smoking is harmful” days. Polls tell us that Americans in every age group don’t care about sexual orientation and that all but the oldest Americans believe that granting the right to marry to all is long overdue. In fact, I recently heard openly gay former U.S. Representative Barney Frank describe the right to marry as enjoying a tsunami of support, not just on the Eastern seaboard, not just across America, but increasingly, across Europe.

It feels like such a short time ago that I myself did not see any reason to support homosexual marriage. My friend and colleague in the field of responsible investing, Julie Goodridge, sued for the right to marry. I thought it was an awful lot of work and loss of privacy, and there wasn’t anything wrong with living together. But she had been denied the presence of her spouse in the delivery room, and that seemed wrong. She was also denied the benefit of marriage in filing her tax returns, obtaining health care, retirement planning and estate planning. Nobody really cared that Hilary and she were partners, but everyone wanted to deny them the most natural results. So I came around. They won that case. And now Tommy and Brian are married.

These things fill me with great hope. I know in my core that important and positive change can occur. What will be next? Will we use the power of common sense to get our proliferating automatic weapons out of the hands of killers? Will we use it to get help, rather than prison sentences, for the addicted? Will we seek systemic means of providing the highest quality ­education, food, shelter and health care to our ­population? There is such a thing as the power of the people, and when you see it used, it is thrilling.