Coco Chanel was wearing beach pyjamas by 1918, and by the mid-1920s rich women had copied her. The BBC notes the look was shocking for its suggestion of the boudoir, yet a 1927 poster sold Venice's Lido as "the beach of sunshine and pyjamas". Women in trousers were a beach idea first, and a street idea much later. That is the lineage I think about when someone asks what to wear with silk pants in October, with a cold evening ahead and a dinner on the calendar.

Then Irene Galitzine, a Russian designer working in Rome, showed her silk trousers at the Palazzo Pitti in 1960. Diana Vreeland, then at Harper's Bazaar, called them palazzo pajamas, and the name stuck. Six years later Yves Saint Laurent sent out Le Smoking, the female tuxedo. So the answer has always been the same: let the trouser be the soft thing and make everything else quiet and sharp.

Here is the cast of trousers. The Toteme black satin wide-leg is the one I would wear to a late dinner with a fine sweater, because the drape does the talking. The Khaite Rohen in bright green is a statement, so I would keep the top plain and dark. Joseph's Dijon in cream silk-satin and The Park's Rebecca in white are the straight-leg pair, calmer and better in daylight. Sablyn's cinnabar pull-ons and the Röhe in night are the relaxed ones, with covered elastic waists for long days.

Hold the fabric to a window before you commit. Silk-satin shows its sheen at the hip and knee, and you want that to look like light, not strain. Check the label too: the Joseph, The Park, Sablyn and Röhe pairs are silk, while the Toteme is viscose and La Ligne's Colby is acetate and polyester.

Britannica describes satin as a smooth fabric with a lustrous face and a dull back, and that contrast is your whole styling plan. A shiny trouser wants a matte top. Cashmere is the most obvious matte, which is why a fine knit sits so well on top of silk pants once the weather turns.

I would start from black. The Arch4 Ivy and Joseph's Cashair are both round-neck black cashmere in a fine, light gauge, and they tuck cleanly into a high waist. For something softer, Khaite's Mae in brown and Lisa Yang's Heidi turtleneck in brown look rich against cream or green satin. Theory's relaxed V-neck in ivory and Anine Bing's heather gray Lee crew are the daytime pair, with ribbed trim that keeps the shape. Jenni Kayne's Boyd in oatmeal has a two-way zip, so you can open it at the neck for an evening, and Le Kasha's Chypre has elbow-length sleeves that show a bracelet.

Test the knit the way you would test a silk lining. Rub a small patch against the trouser fabric: if it grabs or pills on the thigh, wear it tucked or choose something closer in weave. Hem length matters too. A sweater that ends at the hip bone and sits over the waistband looks easy, while a longer one flattens the drape.

What I would skip: a chunky, heavily textured knit over fluid satin. It fights the trouser and hides the one thing you bought them for.

A boat neck is the cleanest answer to a drapey trouser, because it draws a straight line across the collarbone and leaves the waist alone. Fitted long sleeves do the same job in a different way. Both are about having one tidy shape against all that movement below.

The black ones come first. Reformation's Brianna is a cashmere boat-neck top with ribbed trim, and Enza Costa's Silk Knit Boat Neck is a lightweight ribbed knit made in the USA. Enza Costa's fine cotton version in white is the crisp option with cream or navy pants. Vince's Draped Slash Top has ruching at the waist, so it works untucked and gives you some shape without a belt. If you prefer a turtleneck, Nili Lotan's Keria in ecru, Agolde's Pascale in dark gray and The Park's Joyce bodysuit in burgundy are all close-fitting jersey. Jil Sander's wool-jersey bodysuit in black gives a seamless line under a blazer, and a bodysuit cannot untuck.

Try each top sitting down. Boat necks can slide back, and a bodysuit snap can pinch, so lift your arms and check the neckline holds. Then look at the shoulder seam, because on a fitted top it should land at the edge of your shoulder.

In our fashion dreams, she is walking into a fall dinner in black silk pants and a black boat neck, with one good earring. What I would skip: a top with a print or a big ruffle, which turns a quiet outfit into a loud one.

Yves Saint Laurent's team famously pinned the sleeves of Le Smoking on a bent arm, hand on hip, as the former technical director Jean-Pierre Derbourd explained. I think about that whenever I choose a blazer for silk trousers: the jacket should look right when the wearer is moving, not standing still.

Start from the black wool ones. Theory's Etiennette in grain de poudre has a tailored fit, and Nili Lotan's Diane is a stretch-wool twill with sharp tailoring. Toteme's wool-blend blazer has a clean, structured line, Skall's Barbara is a wool twill with a sharp shape, and rag & bone's Mercer Regalia adds ribbon trim and a hook-and-eye placket. Saint Laurent's own Tube blazer is the nod to the 1966 original: grain de poudre wool trimmed in satin, which you can wear closed over nothing but a fine top. The Favorite Daughter Headlines has padded shoulders and a pleated waist, and TWP's Double Take has an asymmetrical collar and a silk-blend lining.

Check the shoulder first, since padding that overhangs your arm will not read as sharp. Then button it and look for pulling at the waist, and check that the hem hits just below the hip.

What I would skip: a blazer in a shiny fabric over shiny trousers. Pair satin with wool and the light does the work.

The shoe decides the mood of silk pants more than any other piece. A pointed slingback says dinner, a loafer says Tuesday, and a mule says you are in no hurry. The hem is where this all gets settled, so choose the shoe before you hem the pants.

For loafers, the Aeyde Jasper in tan suede and The Row's soft leather pair in brown are slim and slipper-like, and they let the trouser break gently over the top. Slingbacks are the evening move: Manolo Blahnik's Maysli 70 in dark brown suede has a buckle, Gianvito Rossi's Ascent 55 in beige is lower and quieter, and Loeffler Randall's Katerina has a pointed toe, a block heel and a partly elasticated strap that keeps the heel in place. For mules, the Staud Brynn 70 in dark brown and Toteme's Bar 85 in snake-effect leather give height. Dolce Vita's Gema is a black pointed-toe flat with a cushioned footbed, the one I would reach for on a long travel day.

Test the hem standing in the exact shoe. Silk should skim the floor at the back without dragging, and a wide leg wants a heel or a platform to hold that line. Flats call for a slightly shorter hem.

What I would skip: a thick chunky sole under a thin silk trouser. It makes the pants look short and the silk look wasted.

I would choose the trouser first, because everything else answers it. Pick the one you will actually wear in October, so black satin or a deep cinnabar, and hold the fiber label up before anything else.

Then add a matte top, a sharp jacket and a shoe that fits your hem. That is three decisions, and each one is already in the lineage: Chanel's ease on the sand, Galitzine's drape in Rome, Saint Laurent's tailoring in Paris.

If someone asks what to wear with silk pants, tell them to dress as if the pants were already doing the talking. The rest of the outfit gets to be calm.