Eileen Collins looks great in blue. That's the color of the NASA flight suit, and Collins, the agency's first female pilot-astronaut, was wearing one when she deplaned after her stint commanding the shuttle Discovery. It was thrilling for me to watch a woman lead a space mission, and it was difficult for Collins to get there in the first place. That makes us both part of a vanishing breed.

The generation of women who have watched the world change from black-and-white to Technicolor as surely as Dorothy did when she went from Kansas to Oz is graying now, and those who come after us will never have the sense of amazement we have known. I'm a 53-year-old woman who found the closest thing to a childhood role model in biographies of Elizabeth I, and I will always get a kick out of women warriors who beat the odds. Look at Collins, who had to play the angles because she was banned as a woman from flying fighter jets, who became an ace at flying the training jets the fighter pilots had to master instead. But the odds have changed, and the era of the firsts, the onlys, the barrier breakers, is almost gone. That's the good news and the bad, all at the same time.

I once heard Claudia Kennedy, the first and only female three-star general in the Army, talk about the question of critical mass, of how many members of any group you need inside the tent to speak out, to speak up, to make changes, to raise hell. But maybe there's also a critical mass at which we think things are just dandy, when dandy is still a ways off. Is it 14 female members of the Senate? Is it two women on the Supreme Court? Is it one? There was once a wow! factor to appointing a woman; that's one reason Ronald Reagan chose Sandra Day O'Connor. But the price of progress is that the wow! factor has dissipated, and so George W. Bush didn't feel the need to replace O'Connor with another woman. Some conservatives dismissed the notion that he should, rejecting as "identity politics" what some of us like to call "simple fairness."

O'Connor herself, usually so judicious in her public comments, openly expressed regret that the Bush nominee to the high court was not female. The retiring justice knows how important it can be when a woman appears in a position of power where her sex has been absent heretofore. She has spoken proudly of how her elevation to the high court opened the bench up to female judicial candidates nationwide. Yet when she was chosen almost 24 years ago, one of the letters she received read: "Back to your kitchen and home female! This is a job for a man and only he can make the rough decisions. Take care of your grandchildren and husband."

That sort of ignorant twaddle made the early stages of the movement for women's equality simpler. Fighting flagrant bigotry is a big-muscle motion; it requires less finesse than sidling around tokenism or dealing with entrenched custom. Young women today encounter the subtle sexism of far-enough rather than the raw stuff of no-way. At the sort of firms from which the job-seeking O'Connor was summarily turned away after her graduation from Stanford Law more than a half century ago, there are now plenty of female lawyers. But if those firms are like other American institutions, most power is concentrated in a group of white men, white men who hire those who remind them of themselves when young.

It's a pleasure to have The Woman in corporations, newsrooms, universities and legislative bodies replaced by a few, several, a fair number, a decent amount. But novelty was once a powerful goad to do the right thing. A boardroom without women quickly took on a prehistoric air. Yet by some trick of entitlement mathematics, a board with two women out of 20 members has come to feel just right. That's not wrong in the same way male-only organizations once were. It's just wrong in a different way. This fall there will be a TV drama in which the president dies and his female second ascends to the pinnacle of power. The first thing advisers do is ask her to step down for the good of the nation. Of course. Because who knows: she might go on estrogen overload and send the country to war on the basis of weapons of mass destruction and ties to terrorist organizations that don't exist.

There's a lot of carping today about younger women, about how they take for granted the rights and opportunities that still seem so shiny new. But that was the point of the exercise, wasn't it, a generation of girls who are asked what they want to be when they grow up so often and insistently they may be a little sick of the question. They will never feel the frisson I do when they look at O'Connor, or Collins. They're already on to the second female secretary of State; they cut their teeth on Sally Ride. I've been exhilarated by a sense of possibility. Those younger women have moved on to probability. But they must be sure not to confuse that with certainty, or, for that matter, complacency.