After all, once you don't have to go to the office anymore, who cares how you look?

Corinne Richardson of St. Louis does. When she agreed to run a discussion group focused on retirement issues, Richardson found herself faced with a gaggle of men and women aged 50 to 75, many attired in Bermuda shorts, worn-out sneakers and old T-shirts, "usually with some sort of writing on the front." ("My grandson went to Harvard and all I got was...")

She invited them to perform an experiment. For the next month, whenever they left their houses, they'd follow a strict dress code: plain trousers, khakis or full-length jeans (no cut-offs or shorts); shirts without writing on them; real shoes; navy, black, tweed, plaid or madras blazers. Hardly the height of fashion, but a step up from souvenir T's and shorts. She also asked them to pay particular attention to how the general public — neighbors, passers-by, grocery store clerks, salespeople, gas station attendants, etc. — responded to them.

They reported back a month later that "much to their surprise, they were treated with more kindness, assistance, friendliness and, most important, with more respect than they had thought possible."

So: Even when you no longer need to telegraph your professional competence with your clothes, and long after you've stopped believing the way you dress or do your hair will beguile Prince Charming or catch the eye of a talent scout who'll make you a star, there's still a reason not to go out looking like an unmade bed.

I have to admit that, when I first read this, it rankled. Even if you're the nicest, kindest, smartest, most conscientious solid citizen imaginable, you still have to dress up or people will write you off as a no-account nobody they can afford to ignore? It's unfair and undemocratic. It's elitist, classist and looksist.

But so is the world we live in. You have an inalienable right to leave the house looking like an unmade bed — but do you really want to exercise it if it means being dismissed, disregarded and disrespected by the general public?

In "Dressing Nifty After Fifty: The Definitive Guide to a Simple, Stylish Wardrobe," Richardson argues that how you dress is a "reflection of how you feel about yourself" and "an invitation to be treated in a certain way by others." You're not going to walk around wearing a sign that says, "Kick me" — so why wear those dumb T-shirts?

You can tell the book was written by a lawyer. It starts with a disclaimer of responsibility, so you can't sue her for any potential unfortunate effects of her fashion advice. It's also not a surprise to learn she took early retirement to follow her passion for the voluntary simplicity movement. Her book is less interested in turning you into a fashion diva than in figuring out what clothes you actually need to live your life, what makes you look better rather than worse, what you can afford to bag up for the Salvation Army, and how you can organize and deploy the clothes you keep.

It grew out of her own discovery that, like many tireless and enthusiastic shoppers, she'd ended up with closets stuffed with pretty clothes, lots of them still unworn, but nothing to wear. Or, anyway, not what she needed.

Chapter by chapter, she walks you through the process she developed for herself by trial and error. What do you do — work, volunteering, household chores, socializing, exercise, relaxation, etc. — in a typical two-week period? What clothes, and how many of them, do those activities require? What do you look like? What looks good on you? By the end, you've put together a wardrobe that covers every eventuality that is current, stylish, flattering — and is also small enough to maintain and keep track of without superhuman effort.

You've also picked up all sorts of sensible advice, from how to tell you're wearing too much perfume (if you can smell it yourself, it's too much) to five ways to tie a scarf, to what to wear to a class reunion (jeweltone dress or pantsuit in the latest style, fantastic looking shoes and bag).

Sensible fashion advice? It isn't something you run into all that often, but that doesn't mean it's an oxymoron. We're used to fashion authorities who burble on ecstatically about this season's must-have $1,000 handbag, assure you that every woman can wear a bikini, and urge you to save your lunch money for a divine pair of over-the-knee boots like the ones Johnny Depp wore in those pirate movies.

Right.

Corinne Richardson, by contrast, is not a fashion magazine editor from New York. She's a lawyer from St. Louis with a good haircut, a woman who loves clothes but doesn't want to devote her life to them. Her advice is not wildly original, which may be just as well. She thinks women over 50 shouldn't let their hair grow past their shoulders, and women who need reading glasses should wear them on chains around their necks — unlike Charla Krupp, author of "How Not to Look Old," who wants you to grow your hair long and never wear glasses around your neck because it's like wearing a sign that says "old lady."

Reading Richardson's book won't turn you into Patricia Field or Sarah Jessica Parker — also just as well: Think what your friends would say if you showed up for choir practice in leather pants and Valentine-red hair.

What it will do is help you find the courage to give away all the clothes you know you'll never wear (or, anyway, shouldn't), organize your closet so you can find what you're looking for, and dress in a way that lets you look good to yourself and your friends and neighbors while inviting the respect of strangers. Isn't that what most grown-ups who aren't fashion models or fashion editors want from fashion?