Alpaca, linen and cashmere make the best sweaters in my opinion. Alpaca and linen are great for temperate months, because they are warm when it's cool and cool when it's warm. Cashmere is what I want when the temperature goes down. I like the feel, though I have to admit that merino wool is most of the way there and only half the cost.
I wrote recently about the sleeveless v-neck vest for wear under a jacket. Three other styles of knitwear are the backbone of a cold weather knitwear wardrobe for less formal occasions: the crew neck (cabled or plain), the to-button cardigan, and the rollneck. The crewneck goes over a shirt, with odd trousers. The cardigan is worn informally in place of a jacket. And the rollneck can be worn under a jacket in place of a dress shirt, like the man in the illustration.
Before dyeing, cashmere comes naturally in tones of mid-grey, cafe au lait and a dirty cream. Add navy to that list and those are the colors I prefer.
All cashmere fibre comes from the underhair beneath the exterior coat of the cashmere goat living on the frigid plateaus of Mongolia and China - and it takes the underhair of at least three goats to create one sweater. The best feels soft and smooth, but never slippery or buttery which are signs of over processing.
The Scots, starting with Johnston's of Elgin, have been knitting cashmere the longest but the Italians have closed the quality gap. The best makers are the 16 members of the Scottish Cashmere Club such as Alex Begg and Murray Allen, and a couple independent Italians like Loro Piana and Colombo Cashmere.
I wasn't familiar with Colombo until Jonathan Fischer at Four in Hand lent me a box of their new knits. I was really impressed. The two ply sweaters look like worsted cashmere, smooth and tightly knit.
Unless he lives in an unheated castle in the Hebrides, two ply is all the sweater a man needs. A cabled cashmere crewneck over a chambray shirt, worn with moleskin trousers and moccasins is about as comfortable as it gets on the weekend. Paired perhaps with a polka dotted silk neckerchief and a bit of single malt.