Crist recently spent a weekend with some girlfriends, during which they talked about girl things, like lingerie. "Somehow the topic of slips came up – as in, none of them wore slips. There I was, in my jersey dress -- complete with slip underneath – jaw agape, wondering if their mothers knew." Was she the only one, she wondered, still wearing a slip?

I did the logical thing and asked the Internet. The response was wide ranging and truly impassioned, everything from yes, I always wear a slip to what exactly would a "slip" be again?

How is it possible to get by without a slip these days? Easy. Better clothing design and better undergarments have substantially lessened the need for a slip. Dresses and skirts frequently come fully lined, which wasn't always the case. Day dresses made up through the 1970s often had no lining at all; a slip was a necessity, not just for modesty's sake but for comfort and style. Today, though, most dresses and skirts -- certainly the type you would wear to a more formal event or to the office -- are lined. No slip needed!

Undergarments have also advanced past the basic slip; now instead of just blocking out any views of bras and panties, underwear also holds in our tummies and hoists our breasts and flattens (or pads) our backsides. Underwear can change the whole shape of your body, but for most women, this kind of serious restraint isn't for everyday wear; we save the Spanx for special occasions. Day-to-day, we let it all hang out (or we just suck it in without any extra help).

But are there times when a slip is called for -- a something between what one Friday Style reader called "stunt lingerie" (the piece pictured above) and the full Spanx girdle? Certainly.

A slip -- or any sort of "foundation garment" -- is designed to let your dress or skirt fall properly over your curves. Unlike a shaper, which quite literally changes your shape, a slip prevents pieces from clinging or sticking or bunching. A slip won't compress your gut or tush, but it CAN make you look thinner and more shapely because it lets your clothes hang properly.

A slip is also a good way to avoid various sorts of wardrobe malfunctions, like the skirt that seemed so cute in the dressing room but turns out to be completely see-through in broad daylight. We tend to scoff a little at the whole idea that fashion might want to be a little more modest, but let's face it: we're all tired of pop stars climbing out of limos without any underwear on -- a little modesty isn't a bad thing. A slip is like a little whisper of an insurance policy, guaranteeing that your dress won't ride up or fly open or leave you showing off your everything to the world.

Miguelina found a fantastic cotton slip, which would be perfect under sheer summery skirts. And Sarah at College Candy has some tips on how to wear a slip, including ways to make a visible slip chic.

All slips pictured here are available at Nordstrom.

Susan Wagner writes about fashion at Friday Style and The Working Closet and Fashion Find. Have a pressing style question? Email her at fridaystyle.susan@gmail.com.